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Search: id:A156431
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A156431 Number of nXn arrays of squares of integers, symmetric under 90 degree rotation, with all rows summing to 2. +0
1
1, 0, 2, 0, 12, 0, 90, 0, 810, 0, 8940, 0, 116760, 0, 1756860, 0, 29933820, 0, 569744280, 0, 11981526480, 0, 275893362360, 0, 6903968231160, 0, 186558764792400, 0, 5413973807642400 (list; graph; listen)
OFFSET

2,3
CROSSREFS

Adjacent sequences: A156428 A156429 A156430 this_sequence A156432 A156433 A156434

Sequence in context: A075533 A053814 A095238 this_sequence A067994 A143246 A104014

KEYWORD

nonn

AUTHOR

Ron Hardin (rhhardin(AT)att.net) Feb 09 2009

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Last modified November 8 20:39 EST 2009. Contains 166234 sequences.

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