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A247417
Number of nonisomorphic binary n X n matrices with two 1's per column under row and column permutations.
5
1, 3, 11, 35, 132, 471, 1806, 7042, 28494, 118662, 510517, 2262738, 10337474, 48625631, 235357470, 1171163995, 5986424739, 31403695142, 168913667164, 930739116386, 5249162406890, 30275048671498, 178428441191289, 1073737691984694, 6592909590432719
OFFSET
2,2
MAPLE
Using the uploaded program the call is seq(matrix_marks(n, 2), n=3..15);
PROG
(PARI) \\ See A304942 for Blocks
a(n) = Blocks(n, n, 2); \\ Andrew Howroyd, May 24 2018
CROSSREFS
Column k=2 of A304942.
Sequence in context: A320087 A014335 A147474 * A222286 A119143 A119092
KEYWORD
nonn
AUTHOR
Marko Riedel, Sep 21 2014
EXTENSIONS
Terms a(17) and beyond from Andrew Howroyd, May 23 2018
STATUS
approved