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A111602
Third column (m=2) of unsigned triangle A111595.
1
1, 6, 42, 300, 2475, 22050, 220500, 2381400, 28279125, 360186750, 4970577150, 73045872900, 1150472498175, 19174541636250, 339663308985000, 6333077180430000, 124682456989715625, 2572020969902133750
OFFSET
2,2
FORMULA
E.g.f.: (1/sqrt(1-x^2))*((x/(1-x))^2)/2!.
a(n) = (n!/2!)*Sum_{k=0..floor((n-2)/2)} binomial(2*k, k)*(n-2*k-1)/(4^k), n >= 2.
CROSSREFS
Sequence in context: A155196 A147838 A127628 * A299916 A091164 A004982
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Aug 23 2005
STATUS
approved