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A318591
Number of n-member subsets of [3*n] whose elements sum to a multiple of three.
2
1, 1, 5, 30, 165, 1001, 6198, 38760, 245157, 1562331, 10015005, 64512240, 417226230, 2707475148, 17620076360, 114955810530, 751616304549, 4923689695575, 32308782871911, 212327989773900, 1397281501935165, 9206478467531865, 60727722660586800, 400978991944396320
OFFSET
0,3
LINKS
EXAMPLE
a(2) = 5: {1,2}, {1,5}, {2,4}, {3,6}, {4,5}.
CROSSREFS
Column k=3 of A318557.
Sequence in context: A003731 A343362 A055838 * A094972 A084158 A111469
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 29 2018
STATUS
approved