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 A066383 a(n) = Sum_{k=0..n} C(n*(n+1)/2,k). 1
 1, 2, 7, 42, 386, 4944, 82160, 1683218, 40999516, 1156626990, 37060382822, 1328700402564, 52676695500313, 2287415069586304, 107943308165833912, 5499354613856855290, 300788453960472434648, 17577197510240126035698, 1092833166733915284972350 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Harry J. Smith, Table of n, a(n) for n = 0..100 FORMULA a(n) = 2^(n*(n+1)/2) - binomial(n*(n+1)/2,n+1)*2F1(1,(-n^2+n+2)/2;n+2;-1), where 2F1(a,b;c;x) is the hypergeometric function. - Ilya Gutkovskiy, May 06 2016 MATHEMATICA f[n_] := Sum[Binomial[n (n + 1)/2, k], {k, 0, n}]; Array[f, 21, 0] (* Vincenzo Librandi, May 06 2016 *) PROG (PARI) { for (n=0, 100, a=0; for (k=0, n, a+=binomial(n*(n + 1)/2, k)); write("b066383.txt", n, " ", a) ) } \\ Harry J. Smith, Feb 12 2010 CROSSREFS Sequence in context: A317349 A158840 A038052 * A011802 A007065 A005130 Adjacent sequences:  A066380 A066381 A066382 * A066384 A066385 A066386 KEYWORD nonn AUTHOR N. J. A. Sloane, Dec 23 2001 STATUS approved

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Last modified October 14 07:11 EDT 2019. Contains 327995 sequences. (Running on oeis4.)