A108479 Antidiagonal sums of number triangle A086645.

1, 1, 2, 7, 17, 44, 117, 305, 798, 2091, 5473, 14328, 37513, 98209, 257114, 673135, 1762289, 4613732, 12078909, 31622993, 82790070, 216747219, 567451585, 1485607536, 3889371025, 10182505537, 26658145586, 69791931223, 182717648081

Offset

0,3

Links

Table of n, a(n) for n=0..28.

Index entries for linear recurrences with constant coefficients, signature (2,1,2,-1).

Formula

G.f.: (1 - x - x^2)/(1 - 2*x - x^2 - 2*x^3 + x^4).

a(n) = 2*(n-1) + a(n-2) + 2*a(n-3) - a(n-4).

a(n) = Sum_{k=0..floor(n/2)} C(2*(n-k), 2*k).

a(n) = Sum_{k=0..floor(n/2)} Sum_{j=0..n-k} C(2*(n-2*k), j) * C(2*k, j).

a(n) = A005252(2*n). - Seiichi Manyama, Aug 11 2024

Mathematica

LinearRecurrence[{2, 1, 2, -1}, {1, 1, 2, 7}, 30] (* Harvey P. Dale, Jun 01 2021 *)

Crossrefs

Cf. A005252, A051286, A086645, A182890.

Sequence in context: A175120 A239357 A106910 * A178441 A014742 A367687

Adjacent sequences: A108476 A108477 A108478 * A108480 A108481 A108482

Keyword

easy,nonn

Author

Paul Barry, Jun 04 2005

Status

approved