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A077828
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Expansion of 1/(1-3*x-3*x^2-3*x^3).
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1
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1, 3, 12, 48, 189, 747, 2952, 11664, 46089, 182115, 719604, 2843424, 11235429, 44395371, 175422672, 693160416, 2738935377, 10822555395, 42763953564, 168976333008, 667688525901, 2638286437419, 10424853888984, 41192486556912, 162766880649945, 643152663287523
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n)=sum{k=0..n, T(n-k, k)3^(n-k)}, T(n, k) = trinomial coefficients (A027907). - Paul Barry (pbarry(AT)wit.ie), Feb 15 2005
a(n)=sum{k=0..n, sum{i=0..floor((n-k)/2), C(n-k-i, i)C(k, n-k-i)}*3^k}; - Paul Barry (pbarry(AT)wit.ie), Apr 26 2005
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CROSSREFS
| Partial sums of S(n, x), for x=1...12, A021823, A000217, A027941, A061278, A089817, A053142, A092521, A076765, A092420, A097784, A097826-7.
Cf. A071675.
Sequence in context: A151166 A151167 A064562 * A002001 A164346 A113956
Adjacent sequences: A077825 A077826 A077827 * A077829 A077830 A077831
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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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