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A077995
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Expansion of (1-x)/(1-2*x-2*x^2-x^3).
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2
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1, 1, 4, 11, 31, 88, 249, 705, 1996, 5651, 15999, 45296, 128241, 363073, 1027924, 2910235, 8239391, 23327176, 66043369, 186980481, 529374876, 1498754083, 4243238399, 12013359840, 34011950561, 96293859201, 272624979364, 771849627691, 2185243073311, 6186810381368
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Equals INVERT transform of (1, 3, 4, 4, 4,...). [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Jan 03 2009]
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FORMULA
| a(n)=sum(m=1..n, sum(i=0..n-m, binomial(m+i-1,m-1)*sum(j=0..m, binomial(j,n-3*m+2*j-i)*binomial(m,j)*2^(n-3*m+2*j-i)))), n>0, a(0)=1. [From Vladimir Kruchinin kru(AT)ie.tusur.ru, May 12 2011]
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PROG
| (Maxima)
a(n):=sum(sum(binomial(m+i-1, m-1)*sum(binomial(j, n-3*m+2*j-i)*binomial(m, j)*2^(n-3*m+2*j-i), j, 0, m), i, 0, n-m), m, 1, n); [From Vladimir Kruchinin kru(AT)ie.tusur.ru, May 12 2011]
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CROSSREFS
| Sequence in context: A192312 A004080 A027115 * A176573 A076730 A084757
Adjacent sequences: A077992 A077993 A077994 * A077996 A077997 A077998
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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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