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 A180844 a(n) = (27^n-2^n)/25 6
 0, 1, 29, 787, 21257, 573955, 15496817, 418414123, 11297181449, 305023899379, 8235645283745, 222362422662139, 6003785411879801, 162102206120758723, 4376759565260493713, 118172508262033346635, 3190657723074900391913 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS 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. LINKS FORMULA a(n) = (27^n-2^n)/25 GF(x) = x/((27*x-1)*(2*x-1)) MATHEMATICA (#[[1]]-#[[2]])/25&/@Partition[Riffle[27^Range[0, 20], 2^Range[0, 20]], 2]  [From Harvey P. Dale, Jan. 22, 2011] CROSSREFS 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 KEYWORD easy,nonn AUTHOR Johannes W. Meijer, Sep 21 2010 STATUS approved

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Last modified June 19 01:40 EDT 2013. Contains 226359 sequences.