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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Table of n, a(n) for n=2..19.

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

Adjacent sequences:  A111599 A111600 A111601 * A111603 A111604 A111605

KEYWORD

nonn,easy

AUTHOR

Wolfdieter Lang, Aug 23 2005

STATUS

approved

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Last modified June 18 13:35 EDT 2021. Contains 345112 sequences. (Running on oeis4.)