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A257975
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Heptagonal numbers (A000566) that are the sum of five consecutive heptagonal numbers.
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2
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970, 3940, 219246804790, 205684244417408273530, 11480068853945505053489115880, 47065929034956905708053692550, 2626939693541678540279445026253849400, 2464437767031050248773603452558570281788774040, 137550230606703955058365608367051590003016395627772390
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OFFSET
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1,1
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LINKS
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FORMULA
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G.f.: -10*x*(211462*x^8 +198379896430716*x^7 +11072383489254815935515*x^6 +34322119735654912553073*x^5 -14213722750292211889419959*x^4 +20568424419816146874*x^3 +21924680085*x^2 +297*x +97) / ((x -1)*(x^2 -1860498*x +1)*(x^2 +1860498*x +1)*(x^4 +3461452808002*x^2 +1)).
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EXAMPLE
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970 is in the sequence because H(20) = 970 = 112 + 148 + 189 + 235 + 286 = H(7)+...+H(11).
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PROG
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(PARI) Vec(-10*x*(211462*x^8 +198379896430716*x^7 +11072383489254815935515*x^6 +34322119735654912553073*x^5 -14213722750292211889419959*x^4 +20568424419816146874*x^3 +21924680085*x^2 +297*x +97) / ((x -1)*(x^2 -1860498*x +1)*(x^2 +1860498*x +1)*(x^4 +3461452808002*x^2 +1)) + O(x^20)) \\ Colin Barker, May 15 2015
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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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