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 A137647 a(n) = Sum_{k=0..n} C(k(k+1), k) * C(k(k+1), n-k). 1
 1, 2, 19, 312, 7710, 254226, 10490141, 519862812, 30075235131, 1989376821840, 148089577059957, 12251856625291758, 1115218087275339166, 110758226370052793778, 11918195995470354683205 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Harvey P. Dale, Table of n, a(n) for n = 0..333 MATHEMATICA Table[Sum[Binomial[k(k+1), k]Binomial[k(k+1), n-k], {k, 0, n}], {n, 0, 20}] (* Harvey P. Dale, Dec 11 2018 *) PROG (PARI) a(n)=sum(k=0, n, binomial(k*(k+1), k)*binomial(k*(k+1), n-k)) CROSSREFS Sequence in context: A094476 A304637 A119773 * A233107 A187659 A308330 Adjacent sequences:  A137644 A137645 A137646 * A137648 A137649 A137650 KEYWORD nonn AUTHOR Paul D. Hanna, Jan 31 2008 STATUS approved

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Last modified August 3 17:26 EDT 2020. Contains 336200 sequences. (Running on oeis4.)