login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A154921 Triangle read by rows, T(n,k) = C(n,k)*sum(j=0..n-k, E(n-k,j)*2^j), where E(n,k) are the Eulerian numbers A173018(n,k), n>=0, 0<=k<=n. 13
1, 1, 1, 3, 2, 1, 13, 9, 3, 1, 75, 52, 18, 4, 1, 541, 375, 130, 30, 5, 1, 4683, 3246, 1125, 260, 45, 6, 1, 47293, 32781, 11361, 2625, 455, 63, 7, 1, 545835, 378344, 131124, 30296, 5250, 728, 84, 8, 1, 7087261, 4912515, 1702548, 393372, 68166, 9450, 1092, 108, 9, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Old name was: Matrix inverse of A154926.

A000670 appears in the first column. A052882 appears in the second column. A000027 and A045943 appear as diagonals. An alternative to calculating the matrix inverse of A154926 is to move the term in the lower right corner to a position in the same column and calculate the determinant instead, which yields the same answer.

Matrix inverse of (2*I - P), where P is Pascal's triangle and I the identity matrix. See A162312 for the matrix inverse of (2*P - I) and some general remarks about arrays of the form M(a) := (I - a*P)^-1 and their connection with weighted sums of powers of integers. The present array equals 1/2*M(1/2). - Peter Bala, Jul 01 2009

The values in this triangle can be seen as permanents of the Pascal triangle analogous to the method in the Redheffer matrix. The elements satisfy T(n,k)/T(n,k-1)*k=T(n-1,k)/T(n,k)*n which converges to log(2) as n-->infinity and k-->0. More generally to calculate log(x) multiply the negative values in A154926 with 1/(x-1) and calculate the matrix inverse. Then T(n,k)/T(n,k-1)*k and T(n-1,k)/T(n,k)*n in the resulting triangle converge to log(x). - Mats Granvik, Aug 11 2009

This method for calculating log(x) converges faster than the Taylor series when x is greater than 5 or so. See chapter on Taylor series in Spiegel for comparison. - Mats Granvik, Aug 11 2009

Exponential Riordan array [1/(2-exp(x)),x]. - Paul Barry, Apr 06 2011

T(n,k) is the number of ordered set partitions of {1,2,...,n} such that the first block contains k elements.  For k=0 the first block contains arbitrarily many elements. - Geoffrey Critzer, Jul 22 2013

A natural (signed) refinement of these polynomials is given by the Appell sequence e.g.f. e^(xt)/ f(t) = exp[tP.(x)] with the formal Taylor series f(x) = 1 + x[1] x + x[2] x^2/2! + ... and with raising operator R = x - d[log(f(D)]/dD (cf. A263634). - Tom Copeland, Nov 06 2015

REFERENCES

Murray R. Spiegel, Mathematical handbook, Schaum's Outlines, p. 111.

LINKS

Alois P. Heinz, Rows n = 0..140, flattened

R. B. Nelsen, Problem E3062, Amer. Math. Monthly, Vol. 94, No. 4 (Apr., 1987), 376-377.

R. B. Nelsen and H. Schmidt, Jr., Chains in Power Sets, Mathematics Magazine, Vol. 64, No. 1 (Feb., 1991), 23-31.

FORMULA

From Peter Bala, Jul 01 2009: (Start)

TABLE ENTRIES

(1)... T(n,k) = binomial(n,k)*A000670(n-k).

GENERATING FUNCTION

(2)... exp(x*t)/(2-exp(t)) = 1 + (1+x)*t + (3+2*x+x^2)*t^2/2! + ....

PROPERTIES OF THE ROW POLYNOMIALS

The row generating polynomials R_n(x) form an Appell sequence. They appear in the study of the poset of power sets [Nelsen and Schmidt].

The first few values are R_0(x) = 1, R_1(x) = 1+x, R_2(x) = 3+2*x+x^2 and R_3(x) = 13+9*x+3*x^2+x^3.

The row polynomials may be recursively computed by means of

(3)... R_n(x) = x^n + sum {k = 0..n-1} binomial(n,k)*R_k(x).

Explicit formulas include

(4)... R_n(x) = 1/2*sum {k = 0..inf}(1/2)^k*(x+k)^n,

(5)... R_n(x) = sum {j = 0..n} sum {k = 0..j} (-1)^(j-k)*binomial(j,k) *(x+k)^n,

and

(6)... R_n(x) = sum {j = 0..n} sum{k = j..n} k!*Stirling2(n,k) *binomial(x,k-j).

SUMS OF POWERS OF INTEGERS

The row polynomials satisfy the difference equation

(7)... 2*R_m(x) - R_m(x+1) = x^m,

which easily leads to the evaluation of the weighted sums of powers of integers

(8)... sum {k = 1..n-1} (1/2)^k*k^m = 2*R_m(0) - (1/2)^(n-1)*R_m(n).

For example, m = 2 gives

(9)... sum {k = 1..n-1} (1/2)^k*k^2 = 6 - (1/2)^(n-1)*(n^2+2*n+3).

More generally we have

(10)... sum {k=0..n-1} (1/2)^k*(x+k)^m = 2*R_m(x)-(1/2)^(n-1)*R_m(x+n).

RELATIONS WITH OTHER SEQUENCES

Sequences in the database given by particular values of the row polynomials are

(11)... A000670(n) = R_n(0)

(12)... A052841(n) = R_n(-1)

(13)... A000629(n) = R_n(1)

(14)... A007047(n) = R_n(2)

(15)... A080253(n) = 2^n*R_n(1/2).

This last result is the particular case (x = 0) of the result that the polynomials 2^n*R_n(1/2+x/2) are the row generating polynomials for A162313.

The above formulas should be compared with those for A162312.

(End)

... A151919 = R_n(1/3)*3^n*(-1)^n

... A052882 = [x^1]R_n(x)

... A045943 = [x^(n-1)]R_n+1(x)

... A099880 = [x^n]R_2n(x). - Peter Luschny, Jul 15 2012

The coefficients in ascending order of x^i of the polynomials p{0}(x) = 1 and p{n}(x) = sum_{k=0..n-1} binomial(n,k)*p{k}(0)*(1+x^(n-k)). - Peter Luschny, Jul 15 2012

EXAMPLE

From Peter Bala, Jul 01 2009: (Start)

Triangle begins

==============================================

n\k|.....0.....1.....2.....3.....4.....5.....6

==============================================

0..|.....1

1..|.....1.....1

2..|.....3.....2.....1

3..|....13.....9.....3.....1

4..|....75....52....18.....4.....1

5..|...541...375...130....30.....5.....1

6..|..4683..3246..1125...260....45.....6.....1

...

(End)

From Mats Granvik, Aug 11 2009: (Start)

Row 4 equals 75,52,18,4,1 because permanents of:

1,0,0,0,1..1,0,0,0,0..1,0,0,0,0..1,0,0,0,0..1,0,0,0,0

1,1,0,0,0..1,1,0,0,1..1,1,0,0,0..1,1,0,0,0..1,1,0,0,0

1,2,1,0,0..1,2,1,0,0..1,2,1,0,1..1,2,1,0,0..1,2,1,0,0

1,3,3,1,0..1,3,3,1,0..1,3,3,1,0..1,3,3,1,1..1,3,3,1,0

1,4,6,4,0..1,4,6,4,0..1,4,6,4,0..1,4,6,4,0..1,4,6,4,1

are:

75.........52.........18.........4..........1

(End)

MAPLE

A154921_row := proc(n) local i, p; p := proc(n, x) option remember; local k;

if n = 0 then 1 else add(p(k, 0)*binomial(n, k)*(1+x^(n-k)), k=0..n-1) fi end:

seq(coeff(p(n, x), x, i), i=0..n) end: for n from 0 to 5 do A154921_row(n) od;

# Peter Luschny, Jul 15 2012

T := (n, k) -> binomial(n, k)*add(combinat:-eulerian1(n-k, j)*2^j, j=0..n-k):

seq(print(seq(T(n, k), k=0..n)), n=0..6); # Peter Luschny, Feb 07 2015

MATHEMATICA

nn = 8; a = Exp[x] - 1;

Map[Select[#, # > 0 &] &,

  Transpose[

   Table[Range[0, nn]! CoefficientList[

Series[x^n/n!/(1 - a), {x, 0, nn}], x], {n, 0, nn}]]] // Grid (* Geoffrey Critzer, Jul 22 2013 *)

PROG

(Sage)

@CachedFunction

def Poly(n, x) : return 1 if n == 0 else add(Poly(k, 0)*binomial(n, k)*(x^(n-k)+1) for k in range(n)

R = PolynomialRing(ZZ, 'x')

for n in (0..6) : print R(Poly(n, x)).coeffs() # Peter Luschny, Jul 15 2012

CROSSREFS

Cf. A000629 (row sums), A000670, A007047, A052822 (column 1), A052841 (alt. row sums), A080253, A162312, A162313.

Cf. A263634.

Sequence in context: A134090 A132845 A129652 * A127126 A161133 A112911

Adjacent sequences:  A154918 A154919 A154920 * A154922 A154923 A154924

KEYWORD

nonn,tabl

AUTHOR

Mats Granvik, Jan 17 2009

EXTENSIONS

A new simpler name given by Peter Luschny, Feb 07 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified April 24 00:59 EDT 2017. Contains 285338 sequences.