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 A077841 Expansion of (1-x)/(1-2*x-3*x^2-2*x^3). 0
 1, 1, 5, 15, 47, 149, 469, 1479, 4663, 14701, 46349, 146127, 460703, 1452485, 4579333, 14437527, 45518023, 143507293, 452443709, 1426445343, 4497236399, 14178696245, 44701992373, 140934546279, 444332462167, 1400872547917, 4416611574893, 13924505717871 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Index entries for linear recurrences with constant coefficients, signature (2,3,2). FORMULA a(n) = sum(k=1..n, sum(i=k..n,(sum(j=0..k, binomial(j,-3*k+2*j+i)* 3^(-3*k+2*j+i)*2^(k-j)*binomial(k,j)))*binomial(n+k-i-1,k-1))), n>0, a(0)=1. - Vladimir Kruchinin, May 05 2011 MATHEMATICA CoefficientList[Series[(1-x)/(1-2*x-3*x^2-2*x^3), {x, 0, 30}], x] (* or *) LinearRecurrence[{2, 3, 2}, {1, 1, 5}, 30] (* Harvey P. Dale, Oct 11 2017 *) PROG (Maxima) a(n):=sum(sum((sum(binomial(j, -3*k+2*j+i)*3^(-3*k+2*j+i)*2^(k-j)*binomial(k, j), j, 0, k))*binomial(n+k-i-1, k-1), i, k, n), k, 1, n); /* Vladimir Kruchinin, May 05 2011 */ CROSSREFS Sequence in context: A331237 A184262 A126944 * A126945 A191641 A199892 Adjacent sequences:  A077838 A077839 A077840 * A077842 A077843 A077844 KEYWORD nonn AUTHOR N. J. A. Sloane, Nov 17 2002 STATUS approved

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Last modified October 1 04:06 EDT 2020. Contains 337441 sequences. (Running on oeis4.)