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A001538
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a(n) = (12n+1)*(12n+11).
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6
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11, 299, 875, 1739, 2891, 4331, 6059, 8075, 10379, 12971, 15851, 19019, 22475, 26219, 30251, 34571, 39179, 44075, 49259, 54731, 60491, 66539, 72875, 79499, 86411, 93611, 101099, 108875, 116939, 125291, 133931, 142859, 152075, 161579, 171371, 181451, 191819
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OFFSET
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0,1
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LINKS
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FORMULA
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G.f.: -(11 + 266*x + 11*x^2)/(x-1)^3 . - R. J. Mathar, Jun 30 2020
Sum_{n>=0} 1/a(n) = (sqrt(3)+2)*Pi/120.
Sum_{n>=0} (-1)^n/a(n) = (4*log(sqrt(2)+1) + sqrt(3)*log(5+2*sqrt(6)))/(60*sqrt(2)).
Product_{n>=0} (1 - 1/a(n)) = (2*sqrt(2)/(sqrt(3)-1))*cos(sqrt(13/2)*Pi/6).
Product_{n>=0} (1 + 1/a(n)) = 2*sqrt(2+sqrt(3))*cos(Pi/sqrt(6)). (End)
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PROG
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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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