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A180844
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a(n) = (27^n-2^n)/25
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6
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0, 1, 29, 787, 21257, 573955, 15496817, 418414123, 11297181449, 305023899379, 8235645283745, 222362422662139, 6003785411879801, 162102206120758723, 4376759565260493713, 118172508262033346635, 3190657723074900391913
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OFFSET
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0,3
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COMMENTS
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The a(n+1) appear in several triangle sums of Nicomachus' table A036561, i.e Ca2(3*n), Ca2(3*n+1)/3, Ca2(3*n+2)/9 and Ca3(n). See A180662 for information about these camel and other chess sums.
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LINKS
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Table of n, a(n) for n=0..16.
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FORMULA
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a(n) = (27^n-2^n)/25
GF(x) = x/((27*x-1)*(2*x-1))
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MATHEMATICA
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(#[[1]]-#[[2]])/25&/@Partition[Riffle[27^Range[0, 20], 2^Range[0, 20]], 2] [From Harvey P. Dale, Jan. 22, 2011]
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CROSSREFS
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Cf. A016153, A016140, A180844, A180845, A180846, A180847, A016185.
Sequence in context: A062560 A135995 A046850 * A159669 A144746 A162831
Adjacent sequences: A180841 A180842 A180843 * A180845 A180846 A180847
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KEYWORD
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easy,nonn
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AUTHOR
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Johannes W. Meijer, Sep 21 2010
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STATUS
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approved
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