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A005999
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Number of paraffins.
(Formerly M1577)
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2
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1, 2, 6, 11, 23, 38, 64, 95, 141, 194, 266, 347, 451, 566, 708, 863, 1049, 1250, 1486, 1739, 2031, 2342, 2696, 3071, 3493, 3938, 4434, 4955, 5531, 6134, 6796, 7487, 8241, 9026, 9878, 10763, 11719, 12710, 13776, 14879, 16061, 17282, 18586, 19931, 21363, 22838, 24404, 26015, 27721, 29474, 31326, 33227, 35231, 37286
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OFFSET
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1,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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G.f.: (x^5+2*x^4+x^3+x^2+1)/((-1+x)^2*(-1+x^2)^2).
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MAPLE
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A005999:=n->1+floor((n-1)/2)+2*(binomial(n+1, 3)-binomial(floor((n+1)/2), 3)-binomial(ceil((n+1)/2), 3))-(n-1)^2: seq(A005999(n), n=1..40); # Wesley Ivan Hurt, Sep 16 2014
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MATHEMATICA
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PROG
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(Magma) [1+Floor((n-1)/2)+2*(Binomial(n+1, 3)-Binomial(Floor((n+1)/2), 3)-Binomial(Ceiling((n+1)/2), 3))-(n-1)^2 : n in [1..50]]; // Wesley Ivan Hurt, Sep 16 2014
(PARI) Vec( (x^5+2*x^4+x^3+x^2+1)/(-1+x)^2/(-1+x^2)^2 + O(x^66) ) \\ Joerg Arndt, Sep 16 2014
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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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