A156436 Number of n X n arrays of squares of integers, symmetric under 90 degree rotation, with all rows summing to 4.

1, 0, 0, 3, 5, 12, 54, 426, 2334, 23280, 152820, 1939740, 14564760, 222925920, 1890254100, 33899743010, 320743643010, 6597891367200, 68944295861280, 1600434039456630, 18309730315533930, 473501454337711800

Offset

1,4

Links

Table of n, a(n) for n=1..22.

Crossrefs

Sequence in context: A291936 A307146 A293599 * A352145 A276735 A099791

Adjacent sequences: A156433 A156434 A156435 * A156437 A156438 A156439

Keyword

nonn

Author

R. H. Hardin Feb 09 2009

Status

approved