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 A187003 Expansion of 1/(1-x-2*x^2-3*x^3-3*x^4-2*x^5-x^6). 1
 1, 1, 3, 8, 20, 50, 126, 317, 798, 2008, 5053, 12716, 32000, 80528, 202649, 509967, 1283334, 3229515, 8127087, 20451846, 51467150, 129517283, 325930746, 820205989, 2064051559, 5194193770, 13071208809, 32893747768, 82777244097, 208309256477, 524211053501 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Seiichi Manyama, Table of n, a(n) for n = 0..2495 Kruchinin Vladimir Victorovich, Composition of ordinary generating functions, arXiv:1009.2565 Index entries for linear recurrences with constant coefficients, signature (1,2,3,3,2,1). FORMULA a(n):=sum(m=1..n, sum(k=m..n, binomial(m,k-m)*sum(j=0..k, binomial(k,j)*binomial(j,n-3*k+2*j)))), a(0)=1. MAPLE seq(coeff(series(1/(1-x-2*x^2-3*x^3-3*x^4-2*x^5-x^6), x, n+1), x, n), n = 0 .. 30); # Muniru A Asiru, Feb 24 2019 PROG (Maxima) a(n):=sum(sum(binomial(m, k-m)*sum(binomial(k, j)*binomial(j, n-3*k+2*j), j, 0, k), k, m, n), m, 1, n) (PARI) Vec(1/(1-x-2*x^2-3*x^3-3*x^4-2*x^5-x^6)+O(x^44)) \\ Joerg Arndt, Mar 04 2011 CROSSREFS Sequence in context: A078053 A122595 A026582 * A101893 A140662 A174198 Adjacent sequences:  A187000 A187001 A187002 * A187004 A187005 A187006 KEYWORD nonn AUTHOR Vladimir Kruchinin, Mar 01 2011 STATUS approved

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Last modified June 12 14:45 EDT 2021. Contains 344957 sequences. (Running on oeis4.)