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A178016
Number of permutations of 2 copies of 1..n with no element e[i>=2]<e[1+floor((i-2)/6)] (6-way heap)
0
1, 3, 30, 360, 6660, 246600, 8856540, 477856260, 43857223200, 3365164845000, 359195930427600, 61064307564624000
OFFSET
1,2
CROSSREFS
Simple 2-way heap A056971
Sequence in context: A144283 A229299 A365158 * A365152 A372087 A357770
KEYWORD
nonn
AUTHOR
R. H. Hardin May 17 2010
STATUS
approved