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A369813
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Expansion of 1/(1 - x^2 - x^7).
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5
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1, 0, 1, 0, 1, 0, 1, 1, 1, 2, 1, 3, 1, 4, 2, 5, 4, 6, 7, 7, 11, 9, 16, 13, 22, 20, 29, 31, 38, 47, 51, 69, 71, 98, 102, 136, 149, 187, 218, 258, 316, 360, 452, 509, 639, 727, 897, 1043, 1257, 1495, 1766, 2134, 2493, 3031, 3536, 4288, 5031, 6054, 7165, 8547, 10196, 12083, 14484, 17114, 20538, 24279, 29085, 34475
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OFFSET
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0,10
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COMMENTS
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Number of compositions of n into parts 2 and 7.
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LINKS
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FORMULA
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a(n) = a(n-2) + a(n-7).
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PROG
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(PARI) my(N=70, x='x+O('x^N)); Vec(1/(1-x^2-x^7))
(PARI) a(n) = sum(k=0, n\7, ((n-5*k)%2==0)*binomial((n-5*k)/2, k));
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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