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 A278884 a(n) = binomial(3*n-1,n) * binomial(3*n,n)/(2*n+1). 3
 1, 2, 30, 672, 18150, 546546, 17672928, 600935040, 21212454582, 770748371250, 28657235757150, 1085694550387200, 41778588391394400, 1628982594897249312, 64234570537702934400, 2557710564063135005184, 102714012593435476016982, 4155894894567674772785250, 169274181059121504574121550, 6935873114065443534326340000, 285716428631735196825345889350, 11826871503027977442890882704050, 491714173272153004121882711232000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Central terms of triangles A278881 and A278882; a(n) = A278881(2*n,n) for n>=0. LINKS Seiichi Manyama, Table of n, a(n) for n = 0..606 FORMULA 4*n^2*(2*n-1)*(2*n+1)*a(n) -9*(3*n-1)^2*(3*n-2)^2*a(n-1)=0. - R. J. Mathar, Dec 02 2016 PROG (PARI) {a(n) = binomial(3*n-1, n) * binomial(3*n, n) / (2*n+1)} for(n=0, 20, print1(a(n), ", ")) CROSSREFS Cf.  A278881, A278882. Sequence in context: A324957 A282733 A160694 * A013525 A270531 A229781 Adjacent sequences:  A278881 A278882 A278883 * A278885 A278886 A278887 KEYWORD nonn AUTHOR Paul D. Hanna, Nov 29 2016 STATUS approved

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Last modified May 20 12:33 EDT 2019. Contains 323422 sequences. (Running on oeis4.)