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 A131820 Row sums of triangle A131819. 2
 1, 6, 16, 33, 59, 96, 146, 211, 293, 394, 516, 661, 831, 1028, 1254, 1511, 1801, 2126, 2488, 2889, 3331, 3816, 4346, 4923, 5549, 6226, 6956, 7741, 8583, 9484, 10446, 11471, 12561, 13718, 14944, 16241, 17611, 19056, 20578, 22179, 23861, 25626 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = a(n-1) + n^2 + 1, n> 1 [From Gary Detlefs, Jun 30 2010] Let M(n) be the n-th square matrix whose (i,j)-entry equals i^2/(i^2+1) if i=j and equals 1 otherwise. Then a(n)=(-1)^(n+1) * gamma(1-i+n) * gamma(1+i+n) * sinh(pi)/pi times the determinant of M(n). [From John M. Campbell, Sep 07 2011] LINKS FORMULA Binomial transform of (1, 5, 5, 2, 0, 0, 0,...). From Alois P. Heinz, May 04 2009: (Start) a(n) = n^3/3 + n^2/2 + 7/6*n - 1. a(n) = -1 + Sum_{k=1..n} (k^2+1). a(n) = A000330(n) + A000027(n) - A000012(n). G.f.: (2*x^3-4*x^2+5*x-1) / (x-1)^4. (End) a(n) = (2n^3 + 3n^2 + 7n - 6)/6, n>0. [Gary Detlefs, Jun 30 2010] a(n) = n^2+a(n-1)+1, n>1. [Gary Detlefs, Jun 29 2010] EXAMPLE a(4) = 33 = (1, 3, 3, 1) dot (1, 5, 5, 2) = (1 + 15 + 15 + 2). a(4) = 33 = sum of row 4 terms of triangle A131819: (13 + 9 + 7 + 4). MAPLE a:= n-> (7+(3+2*n)*n)*n/6-1: seq(a(n), n=1..40);  # Alois P. Heinz, May 04 2009 MATHEMATICA Table[n^3/3 + n^2/2 + 7*n/6 - 1, {n, 100}] CROSSREFS Cf. A131819. A131820(n) = A081489(n) + A005563(n-1), n>0. - Gary Detlefs, Jun 30 2010 Sequence in context: A099399 A118014 A236773 * A266677 A083053 A083046 Adjacent sequences:  A131817 A131818 A131819 * A131821 A131822 A131823 KEYWORD nonn AUTHOR Gary W. Adamson, Jul 18 2007 EXTENSIONS More terms from Alois P. Heinz, May 04 2009 STATUS approved

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Last modified January 20 19:53 EST 2020. Contains 331096 sequences. (Running on oeis4.)