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A156430 Number of n X n arrays of squares of integers, symmetric about both diagonal and antidiagonal, with all rows summing to 2. 0
1, 2, 10, 12, 84, 132, 954, 1728, 13290, 26820, 217500, 481320, 4086600, 9783480, 86549820, 221921280, 2037627900, 5552479800, 52745205240, 151802154000, 1487961422640, 4500041903280, 45412066438200, 143712079822080 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Table of n, a(n) for n=2..25.

CROSSREFS

Sequence in context: A181427 A055697 A055705 * A303356 A299317 A095914

Adjacent sequences:  A156427 A156428 A156429 * A156431 A156432 A156433

KEYWORD

nonn

AUTHOR

R. H. Hardin Feb 09 2009

STATUS

approved

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Last modified December 11 18:46 EST 2019. Contains 329925 sequences. (Running on oeis4.)