A055454 a(n) = A055450(n, n-4).

1, 5, 14, 28, 42, 174, 735, 3155, 13726, 60398, 268361, 1202425, 5427110, 24652698, 112622124, 517102008, 2385026330, 11045344150, 51341255630, 239447037890, 1120163788030, 5254987411850, 24716226207075

Offset: 4

Author

Clark Kimberling, May 18 2000

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 4..500

Crossrefs

Cf. A055450, A055451, A055452, A055453, A055455.

Programs

Magma

[1,5,14,28] cat [Floor(42*HypergeometricSeries2F1(8-n,11/2,7,-4)): n in [8..40]]; // G. C. Greubel, Jan 30 2024

Mathematica

Join[{1,5,14,28}, Table[42*Hypergeometric2F1[8-n,11/2,7,-4], {n,8,40}]] (* G. C. Greubel, Jan 30 2024 *)

SageMath

def A055454(n): return (1,5,14,28)[n-4] if n<8 else 42*hypergeometric([8-n,11/2],[7],-4).simplify()
[A055454(n) for n in range(4,41)] # G. C. Greubel, Jan 30 2024

Formula

a(n) = A055450(n, n-4).

a(n) = 42*Hypergeometric2F1([8-n, 11/2], [7], -4) for n >= 8. - G. C. Greubel, Jan 30 2024

a(n) ~ 128 * 5^(n - 13/2) / (sqrt(Pi) * n^(3/2)). - Vaclav Kotesovec, Aug 09 2025