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A014773
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Squares of odd heptagonal numbers.
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5
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1, 49, 3025, 6561, 35721, 55225, 162409, 219961, 485809, 613089, 1147041, 1385329, 2325625, 2725801, 4239481, 4862025, 7144929, 8059921, 11336689, 12623809, 17147881, 18896409, 24950025, 27258841, 35153041, 38130625, 48205249, 51969681, 64593369, 69272329
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 1/2*(200*n^4-920*n^3+1578*n^2-1196*n+338) for n even.
a(n) = 1/2*(200*n^4-520*n^3+498*n^2-208*n+32) for n odd.
G.f.: x*(1+48*x+2972*x^2+3344*x^3+17262*x^4+5648*x^5+8396*x^6+560*x^7+169*x^8) / ((1-x)^5*(1+x)^4).
(End)
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MATHEMATICA
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Table[SeriesCoefficient[x (1 + 48 x + 2972 x^2 + 3344 x^3 + 17262 x^4 + 5648 x^5 + 8396 x^6 + 560 x^7 + 169 x^8)/((1 - x)^5 (1 + x)^4), {x, 0, n}], {n, 30}] (* Michael De Vlieger, Dec 17 2015 *)
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PROG
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(PARI) Vec(x*(1+48*x+2972*x^2+3344*x^3+17262*x^4+5648*x^5+8396*x^6+560*x^7+169*x^8) / ((1-x)^5*(1+x)^4) + O(x^40)) \\ Colin Barker, Dec 17 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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EXTENSIONS
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STATUS
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approved
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