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 A259335 a(n) = Sum(b(2*n, k)^2*(b(2*n, k + 1) - b(2*n, k - 1)), k = 0 .. n)/(n*b(2*n, n)), where b denotes a binomial coefficient. 1
 1, 7, 61, 611, 6686, 77729, 944245, 11859355, 152893720, 2013070126, 26967817306, 366542344117, 5043651762826, 70138959074461, 984384594022117, 13927418363218955, 198459156018467084, 2845950809029225472, 41044332341739034032, 594983281327999736694 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS H. W. Gould, Problem E2384, Amer. Math. Monthly, 79 (1972), p. 1034. D. Zeitlin & N. J. A. Sloane, Correspondence, 1974 & 1991 MAPLE f:=proc(n) local b; b:=binomial; add(b(2*n, k)^2*(b(2*n, k+1)-b(2*n, k-1)), k=0..n)/(n*b(2*n, n)); end; CROSSREFS Sequence in context: A177132 A077642 A071172 * A127688 A111532 A061634 Adjacent sequences:  A259332 A259333 A259334 * A259336 A259337 A259338 KEYWORD nonn AUTHOR N. J. A. Sloane, Jun 25 2015 STATUS approved

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Last modified December 14 15:08 EST 2019. Contains 329979 sequences. (Running on oeis4.)