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A077841
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Expansion of (1-x)/(1-2*x-3*x^2-2*x^3).
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0
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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; internal format)
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OFFSET
| 0,3
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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. [From Vladimir Kruchinin kru(AT)ie.tusur.ru, May 5 2011]
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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); [From Vladimir Kruchinin kru(AT)ie.tusur.ru, May 5 2011]
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CROSSREFS
| Sequence in context: A089040 A184262 A126944 * A126945 A191641 A199892
Adjacent sequences: A077838 A077839 A077840 * A077842 A077843 A077844
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Nov 17 2002
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