A299500 Triangle read by rows, T(n,k) = [x^k] Sum_{k=0..n} p_{n,k}(x) where p_{n,k}(x) = x^(n-k)*binomial(n,k)*hypergeom([-k, k-n, k-n], [1, -n], 1/x), for 0 <= k <= n.

1, 1, 1, 2, 2, 1, 3, 7, 3, 1, 5, 16, 15, 4, 1, 8, 38, 46, 26, 5, 1, 13, 82, 141, 100, 40, 6, 1, 21, 173, 381, 375, 185, 57, 7, 1, 34, 352, 983, 1216, 820, 308, 77, 8, 1, 55, 701, 2400, 3704, 3101, 1575, 476, 100, 9, 1, 89, 1368, 5646, 10536, 10885, 6804, 2758, 696, 126, 10, 1

Offset

0,4

Links

Table of n, a(n) for n=0..65.

Formula

Let P_{n}(x) = Sum_{k=0..n} p_{n,k}(x) then

2^n*P_{n}(1/2) = A299502(n).

P_{n}(-1) = A182883(n). P_{n}(0) = A000045(n+1).

P_{n}(1) = A108626(n). P_{n}(2) = A299501(n).

The general case: for fixed k the sequence P_{n}(k) with n >= 0 has the generating function ogf(k, x) = (1-2*(k+1)*x + (k^2+2*k-1)*x^2 - 2*(k-1)*x^3 + x^4)^(-1/2). The example section shows the start of this square array of sequences.

These sequences can be computed by the recurrence P(n,k) = ((2-n)*P(n-4,k)-(3-2*n)*(k-1)*P(n-3,k)+(k^2+2*k-1)*(1-n)*P(n-2,k)+(2*n-1)*(k+1)*P(n-1,k))/n with initial values 1, k+1, (k+1)^2+1 and (k+1)^3+4*k+2.

The partial polynomials p_{n,k}(x) reduce for x = 1 to A108625 (seen as a triangle).

Example

The partial polynomials p_{n,k}(x) start:
[0] 1
[1] x,   1
[2] x^2, 2*x+1,        1
[3] x^3, 3*x^2+4*x,    3*x+2,             1
[4] x^4, 4*x^3+9*x^2,  6*x^2+12*x+1,      4*x+3,         1
[5] x^5, 5*x^4+16*x^3, 10*x^3+36*x^2+9*x, 10*x^2+24*x+3, 5*x+4, 1
.
The polynomials P_{n}(x) start:
[0]  1
[1]  1 +    x
[2]  2 +  2*x +    x^2
[3]  3 +  7*x +  3*x^2 +    x^3
[4]  5 + 16*x + 15*x^2 +  4*x^3 +   x^4
[5]  8 + 38*x + 46*x^2 + 26*x^3 + 5*x^4 + x^5
.
The triangle starts:
[0]  1
[1]  1,   1
[2]  2,   2,    1
[3]  3,   7,    3,    1
[4]  5,  16,   15,    4,    1
[5]  8,  38,   46,   26,    5,    1
[6] 13,  82,  141,  100,   40,    6,   1
[7] 21, 173,  381,  375,  185,   57,   7,   1
[8] 34, 352,  983, 1216,  820,  308,  77,   8, 1
[9] 55, 701, 2400, 3704, 3101, 1575, 476, 100, 9, 1'
.
The square array P_{n}(k) near k=0:
......  [k=-2] 1, -1,  2, -7,  17,  -44,  125,  -345,    958,   -2707, ...
A182883 [k=-1] 1,  0,  1, -2,   1,   -6,    7,   -12,     31,     -40, ...
A000045 [k=0]  1,  1,  2,  3,   5,    8,   13,    21,     34,      55, ...
A108626 [k=1]  1,  2,  5, 14,  41,  124,  383,  1200,   3799,   12122, ...
A299501 [k=2]  1,  3, 10, 37, 145,  588, 2437, 10251,  43582,  186785, ...
......  [k=3]  1,  4, 17, 78, 377, 1886, 9655, 50220, 264223, 1402108, ...

Maple

CoeffList := p -> op(PolynomialTools:-CoefficientList(p, x)):
PrintPoly := p -> print(sort(expand(p), x, ascending)):
T := (n, k) -> x^(n-k)*binomial(n, k)*hypergeom([-k, k-n, k-n], [1, -n], 1/x):
P := [seq(add(simplify(T(n, k)), k=0..n), n=0..10)]:
seq(CoeffList(p), p in P); # seq(PrintPoly(p), p in P);
R := proc(n, k) option remember; # Recurrence
if n < 4 then return [1, k+1, (k+1)^2+1, (k+1)^3+4*k+2][n+1] fi; ((2-n)*R(n-4, k)-
(3-2*n)*(k-1)*R(n-3, k)+(k^2+2*k-1)*(1-n)*R(n-2, k)+(2*n-1)*(k+1)*R(n-1, k))/n end:
for k from -2 to 3 do lprint(seq(R(n, k), n=0..9)) od;

Crossrefs

Cf. A000045, A108625, A108626, A182883, A299499, A299501, A299502.

Sequence in context: A334894 A110564 A210791 * A330141 A007441 A289192

Adjacent sequences: A299497 A299498 A299499 * A299501 A299502 A299503

Keyword

nonn,tabl

Author

Peter Luschny, Feb 11 2018

Status

approved