A087487 a(n) = 4*(2^(n^2-n+1)*(n^2-n)-n+3).

8, 68, 3072, 393212, 167772152, 257698037748, 1477743627730928, 32281802128991715308, 2720083094132915643088872, 891316828285473797927369441252, 1142305308877662078276709192428421088, 5749410871496176278677177367167155700760540, 113997127711810427619887416951870075533162738352088

Offset

1,1

References

A. J. Hoffman, On eigenvalues of symmetric (+1, -1) matrices, Israel J. Math., 17 (1974), 69-75 (MR 50#2202).

Links

Table of n, a(n) for n=1..13.

Maple

seq(4*(2^(n^2-n+1)*(n^2-n)-n+3), n=1..10); # Georg Fischer, Dec 03 2024

Mathematica

f[n_]:=Module[{n2n=n^2-n}, 4 (2^(n2n+1) n2n-n+3)]; Array[f, 15]  (* Harvey P. Dale, Mar 24 2011 *)

Crossrefs

Sequence in context: A030992 A091590 A303010 * A178368 A111156 A297633

Adjacent sequences: A087484 A087485 A087486 * A087488 A087489 A087490

Keyword

nonn

Author

N. J. A. Sloane, Oct 24 2003

Extensions

Offset changed to 1 by Georg Fischer, Dec 03 2024

Status

approved