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 A087487 4*(2^(n^2-n+1)*(n^2-n)-n+3). 0
 8, 68, 3072, 393212, 167772152, 257698037748, 1477743627730928, 32281802128991715308, 2720083094132915643088872, 891316828285473797927369441252, 1142305308877662078276709192428421088, 5749410871496176278677177367167155700760540, 113997127711810427619887416951870075533162738352088 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 REFERENCES A. J. Hoffman, On eigenvalues of symmetric (+1, -1) matrices, Israel J. Math., 17 (1974), 69-75 (MR 50#2202). LINKS 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 STATUS approved

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Last modified February 18 21:20 EST 2020. Contains 332028 sequences. (Running on oeis4.)