A183896 Imaginary part of a (-4,-4) Gaussian integer Somos-4 sequence.

0, -1, -2, 0, 0, -128, -1024, 0, 0, -4194304, -134217728, 0, 0, -35184372088832, -4503599627370496, 0, 0, -75557863725914323419136, -38685626227668133590597632, 0, 0, -41538374868278621028243970633760768, -85070591730234615865843651857942052864, 0

Offset: 0

Author

Paul Barry, Jan 07 2011

Keywords

• sign

Comments

Imaginary part of the Hankel transform of A183893(n) + I*A183894(n).

A183895(n) + I*a(n) is a (-4,-4) Gaussian integer Somos-4 sequence.

Links

• G. C. Greubel, Table of n, a(n) for n = 0..112

Crossrefs

Cf. A183893, A183894, A183895.

Programs

Magma

[((-1)^Floor((n+1)/2) -1)*2^Floor((n^2+n-4)/4): n in [0..30]]; // G. C. Greubel, Mar 23 2024

Mathematica

Table[((-1)^Floor[(n+1)/2] -1)*2^(Floor[n*(n+1)/4] -1), {n,0,30}] (* G. C. Greubel, Mar 23 2024 *)

SageMath

[((-1)^((n+1)//2) -1)*2^(n*(n+1)//4 -1) for n in range(31)] # G. C. Greubel, Mar 23 2024

Formula

a(n) = mod(binomial(n+1,2), 2)*A183895(n).