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A156381 Number of 3X3 arrays of squares of integers, symmetric about both diagonal and antidiagonal, with all rows summing to n. 0
1, 2, 2, 1, 2, 0, 2, 0, 2, 4, 0, 2, 1, 0, 0, 0, 2, 2, 4, 2, 0, 0, 2, 0, 2, 4, 0, 3, 0, 0, 0, 0, 2, 4, 4, 0, 4, 0, 2, 0, 0, 4, 0, 2, 2, 0, 0, 0, 1, 2, 4, 5, 0, 0, 4, 0, 0, 4, 0, 2, 0, 0, 0, 0, 2, 0, 6, 2, 2, 0, 0, 0, 4, 2, 0, 3, 2, 0, 0, 0, 0, 8, 2, 2, 0, 0, 2, 0, 2, 4, 0, 0, 0, 0, 0, 0, 2, 2, 2, 7, 4, 0, 4, 0, 0, 0, 0, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n) is nonzero if and only if n = x^2 + 2*y^2 for some integers x and y if and only if n is in A002479. - Michael Somos, Dec 15 2011

LINKS

Table of n, a(n) for n=0..107.

EXAMPLE

All solutions for n=9

...0.0.9...1.4.4...4.4.1...9.0.0

...0.9.0...4.1.4...4.1.4...0.9.0

...9.0.0...4.4.1...1.4.4...0.0.9

CROSSREFS

Cf. A002479.

Sequence in context: A129402 A128580 A104405 * A089077 A203398 A225064

Adjacent sequences:  A156378 A156379 A156380 * A156382 A156383 A156384

KEYWORD

nonn

AUTHOR

R. H. Hardin Feb 09 2009

STATUS

approved

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Last modified December 8 14:38 EST 2019. Contains 329865 sequences. (Running on oeis4.)