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A077840
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Expansion of (1-x)/(1-2*x-3*x^2-3*x^3).
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0
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1, 1, 5, 16, 50, 163, 524, 1687, 5435, 17503, 56372, 181558, 584741, 1883272, 6065441, 19534921, 62915981, 202633048, 652618802, 2101884691, 6769524932, 21802560343, 70219349555, 226154954935, 728375639564, 2345874192598, 7555340168693, 24333429833872
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| a(0)=1 and, for n>=1, a(n)=sum(k=1..n, sum(i=k..n,(sum(j=0..k, binomial(j,-3*k+2*j+i)*3^(-2*k+j+i)*binomial(k,j)))*binomial(n+k-i-1,k-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^(-2*k+j+i)*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: A007806 A037480 A027108 * A007343 A147536 A173871
Adjacent sequences: A077837 A077838 A077839 * A077841 A077842 A077843
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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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