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 A131051 Row sums of triangle A133805. 9
 1, 3, 8, 18, 38, 78, 158, 318, 638, 1278, 2558, 5118, 10238, 20478, 40958, 81918, 163838, 327678, 655358, 1310718, 2621438, 5242878, 10485758, 20971518, 41943038, 83886078, 167772158, 335544318, 671088638, 1342177278, 2684354558 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Last digit of a(n) is 8 for n > 2. - Jon Perry, Nov 19 2012 LINKS FORMULA Binomial transform of [1, 2, 3, 2, 3, 2, 3, ...]. O.g.f.: (1+x^2)/((1-x)(1-2*x)). a(n)=A051633(n-2). - R. J. Mathar, Jun 13 2008 a(n) = 5*2^(n-2)-2, n>1. - Gary Detlefs, Jun 22 2010 a(n) = 2(n-1) + Sum_{i=1..n-1} a(i). - Jon Perry, Nov 19 2012 EXAMPLE a(4) = 18 = sum of row 4 terms of triangle A133805: (7 + 6 + 4 + 1). a(4) = 18 = (1, 3, 3, 1), dot (1, 2, 3, 2) = (1 + 6 + 9 + 2). PROG (Magma) a:=[1]; for n in [2..31] do Append(~a, 2*n-2+&+[a[i]:i in [1..n-1]]); end for; a; // Marius A. Burtea, Oct 15 2019 (Magma) R:=PowerSeriesRing(Integers(), 31); Coefficients(R!( (1+x^2)/((1-x)*(1-2*x)))); // Marius A. Burtea, Oct 15 2019 CROSSREFS Cf. A133805. Cf. A083329, A053209. Sequence in context: A006478 A104187 A051633 * A172265 A258272 A117727 Adjacent sequences: A131048 A131049 A131050 * A131052 A131053 A131054 KEYWORD nonn AUTHOR Gary W. Adamson, Sep 23 2007 EXTENSIONS More terms from R. J. Mathar, Jun 13 2008 STATUS approved

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Last modified November 29 10:31 EST 2022. Contains 358424 sequences. (Running on oeis4.)