A156435 Number of n X n arrays of squares of integers, symmetric about both diagonal and antidiagonal, with all rows summing to 4.

1, 2, 2, 7, 13, 110, 440, 7010, 34814, 709332, 4108632, 100368324, 667960824, 18944759304, 142719383676, 4596517872930, 38710991748930, 1392671800456580, 12976446818207108, 514918876680042334, 5262123025959154234

Offset

1,2

Links

Table of n, a(n) for n=1..21.

Crossrefs

Sequence in context: A362318 A049953 A364313 * A344048 A228432 A298959

Adjacent sequences: A156432 A156433 A156434 * A156436 A156437 A156438

Keyword

nonn

Author

R. H. Hardin Feb 09 2009

Status

approved