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A124996
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a(n) is the constant term in the expansion of Product_{k=1..n} (x^k + 1/x^k)^4.
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3
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1, 6, 44, 426, 4658, 55260, 689508, 8914872, 118374410, 1604658420, 22115171280, 308940507202, 4364729023812, 62256518307724, 895294865045296, 12966655239260890, 188967013096930258, 2769003814616561636, 40773380119956434784, 603008173331642200144
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OFFSET
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0,2
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LINKS
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Ray Chandler, Table of n, a(n) for n = 0..834 (terms < 10^1000)
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FORMULA
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a(n) ~ sqrt(3) * 16^n / (sqrt(2*Pi) * n^(3/2)). - Vaclav Kotesovec, Jan 07 2021
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PROG
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(PARI) a(n) = polcoef(prod(k=1, n, (x^k + 1/x^k)^4), 0); \\ Michel Marcus, Jan 07 2021
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CROSSREFS
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For constant term in expansion of Product_{k=1..n} (x^k + 1/x^k)^q for other values of q see A063865, A047653, A124995.
Sequence in context: A084965 A203159 A279085 * A226045 A001852 A352843
Adjacent sequences: A124993 A124994 A124995 * A124997 A124998 A124999
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Jul 12 2008
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STATUS
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approved
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