

A119900


Triangle read by rows: T(n,k) is the number of binary words of length n with k strictly increasing runs, for 0<=k<=n.


15



1, 0, 2, 0, 1, 3, 0, 0, 4, 4, 0, 0, 1, 10, 5, 0, 0, 0, 6, 20, 6, 0, 0, 0, 1, 21, 35, 7, 0, 0, 0, 0, 8, 56, 56, 8, 0, 0, 0, 0, 1, 36, 126, 84, 9, 0, 0, 0, 0, 0, 10, 120, 252, 120, 10, 0, 0, 0, 0, 0, 1, 55, 330, 462, 165, 11, 0, 0, 0, 0, 0, 0, 12, 220, 792, 792, 220, 12, 0, 0, 0, 0, 0, 0, 1, 78
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OFFSET

0,3


COMMENTS

Sum of entries in row n is 2^n (A000079). Sum of entries in column k is A001906(k+1) (the even indexed Fibonacci numbers). Row n contains 1+floor(n/2) nonzero terms. Sum(k*T(n,k),k=0..n)=(3n+1)*2^(n2)=A066373(n+1) for n>=1. T(n,k)=A034867(n,nk).
Triangle T(n,k), 0<=k<=n, read by rows, given by [0,1/2,1/2,0,0,0,0,0,0,...] DELTA [2,1/2,1/2,0,0,0,0,0,0,...] where DELTA is the operator defined in A084938.  Philippe Deléham, Dec 02 2008
From R. Bagula's comment in A053122 (cf. Damianou link), the columns of this array give the coefficients (mod sign) of the characteristic polynomials for the Cartan matrix of the root system A_n.  Tom Copeland, Oct 11 2014
Odd rows contain the Pascal triangle numbers A091042. See A034867 and A034839 for some relations to tan(x).  Tom Copeland, Oct 15 2014


LINKS

Table of n, a(n) for n=0..85.
A. Collins et al., Binary words, ncolor compositions and bisection of the Fibonacci numbers, Fib. Quarterly, 51 (2013), 130136.
P. Damianou, On the characteristic polynomials of Cartan matrices and Chebyshev polynomials, arXiv preprint arXiv:1110.6620 [math.RT], 2014.
R. Zielinski, Induction and Analogy in a Problem of Finite Sums arXiv:1608.04006 [math.GM], 2016.


FORMULA

T(n,k) = binom(n+1,2kn). G.f.=1/[12tzt(1t)z^2].
From Tom Copeland, Sep 30 2011: (Start)
With K(x,t) = 1/{d/dx{x/[t1+1/(1x)]}} = [t1+1/(1x)]^2/{t[x/(1x)]^2}, the g.f. of A119900 = K(x*t,t)t+1.
From formulas in A134264: K(x,t)d/dx is a generator for A001263. A refinement of A119900 to partition polynomials is given by umbralizing
K(x,t) roughly as K(h.x,h_0) and precisely as in A134264 as
W(x)= 1/{d/dx[f(x)]}=1/{d/dx[x/h(x)]}. (End)
T(n,k) = 2*T(n1,k1)+T(n2,k1)T(n2,k2).  Philippe Deléham, Oct 02 2011
From Tom Copeland, Dec 07 2015: (Start)
An alternate o.g.f. is (1/(x*t)) {1 + 1 / [1  (1/t)[x*t/(1x*t)]^2]} = Sum {n>0} x^(2(n1)+1) t^(n1) / (1t*x)^(2n) = x + 2t x^2 + (t+3t^2) x^3 + ... .
The nth diagonal has elements binomial(2n+1+k,k), starting with k=0 for the first nonvanishing element, with o.g.f. (1x)^(2(n+1)). The first few subdiagonals are shifted versions of A000292, A000389, and A000580. Cf. A049310.
See A034867 for the matrix representation for the infinitesimal generator K(x,t) d/dx for the Narayana polynomials (End)
From Peter Bala, Aug 17 2016: (Start)
Let S(k,n) = Sum_{i = 1..n} i^k. Calculations in Zielinski 2016 suggest the following identity holds involving the pth row elements of this triangle:
Sum_{k = 0..p} T(p,k)*S(2*k + 1,n) = (n*(n + 1)/2)^(p+1).
For example, for row 6 we find S(7,n) + 21*S(9,n) + 35*S(11,n) + 7*S(13,n) = (n*(n + 1)/2)^7.
There appears to be a similar result for the even power sums S(2*k,n) involving A207543. (End)


EXAMPLE

The binary word 1/0/01/01/1/1/01 has 7 strictly increasing runs.
T(5,3)=6 because we have 0/01/01, 01/0/01, 01/01/0, 01/1/01, 01/01/1 and 1/01/01 (the runs are separated by /).
Triangle starts:
1;
0,2;
0,1,3;
0,0,4,4;
0,0,1,10,5;
0,0,0,6,20,6;


MAPLE

T:=(n, k)>binomial(n+1, 2*kn): for n from 0 to 12 do seq(T(n, k), k=0..n) od; # yields sequence in triangular form


MATHEMATICA

Table[Binomial[n + 1, 2 k  n], {n, 0, 12}, {k, 0, n}] // Flatten (* Michael De Vlieger, Aug 21 2016 *)


CROSSREFS

Cf. A000079, A001906, A066373, A034867.
Cf. A098158.  Philippe Deléham, Dec 02 2008
Cf. A000292, A000389, A000580, A001263, A049310, A053122, A134264, A207543.
Sequence in context: A219839 A154312 A236076 * A141097 A278045 A096335
Adjacent sequences: A119897 A119898 A119899 * A119901 A119902 A119903


KEYWORD

nonn,tabl


AUTHOR

Emeric Deutsch, May 27 2006


EXTENSIONS

Keyword tabl added by Philippe Deléham, Jan 26 2010


STATUS

approved



