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A156436 Number of nXn arrays of squares of integers, symmetric under 90 degree rotation, with all rows summing to 4. 0
1, 0, 0, 3, 5, 12, 54, 426, 2334, 23280, 152820, 1939740, 14564760, 222925920, 1890254100, 33899743010, 320743643010, 6597891367200, 68944295861280, 1600434039456630, 18309730315533930, 473501454337711800 (list; graph; refs; listen; history; internal format)
OFFSET

1,4

CROSSREFS

Sequence in context: A002905 A087610 A191636 * A099791 A028268 A171424

Adjacent sequences:  A156433 A156434 A156435 * A156437 A156438 A156439

KEYWORD

nonn

AUTHOR

R. H. Hardin (rhhardin(AT)att.net) Feb 09 2009

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Last modified February 17 14:50 EST 2012. Contains 206050 sequences.