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A133766
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a(n) = (4*n+1)*(4*n+3)*(4*n+5).
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4
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15, 315, 1287, 3315, 6783, 12075, 19575, 29667, 42735, 59163, 79335, 103635, 132447, 166155, 205143, 249795, 300495, 357627, 421575, 492723, 571455, 658155, 753207, 856995, 969903, 1092315, 1224615, 1367187, 1520415, 1684683, 1860375, 2047875, 2247567, 2459835
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OFFSET
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0,1
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REFERENCES
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L. B. W. Jolley, Summation of Series, Dover, 1961.
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LINKS
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Table of n, a(n) for n=0..33.
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
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FORMULA
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G.f.: 3*(5 + 85*x + 39*x^2 - x^3)/(1-x)^4 .
E.g.f: (15 + 300*x + 336*x^2 + 64*x^3)*exp(x) .
Sum_{n>=0} 4/a(n) = (Pi-2)/4. [Jolley, eq. 238]
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>3. - Harvey P. Dale, May 06 2012
Sum_{n>=0} (-1)^n/a(n) = 1/8 + (log(2*sqrt(2)+3) - Pi)/(16*sqrt(2)). - Amiram Eldar, Feb 27 2022
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MAPLE
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seq((4*n+1)*(4*n+3)*(4*n+5), n=0..40);
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MATHEMATICA
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Table[c=4n; (c+1)(c+3)(c+5), {n, 0, 30}] (* or *) LinearRecurrence[{4, -6, 4, -1}, {15, 315, 1287, 3315}, 30] (* Harvey P. Dale, May 06 2012 *)
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PROG
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(PARI) a(n)=(4*n+1)*(4*n+3)*(4*n+5) \\ Charles R Greathouse IV, Oct 16 2015
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CROSSREFS
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Cf. A001539, A154633.
Sequence in context: A105491 A158533 A284070 * A347980 A289951 A112489
Adjacent sequences: A133763 A133764 A133765 * A133767 A133768 A133769
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KEYWORD
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nonn,easy
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AUTHOR
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Miklos Kristof, Jan 02 2008
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STATUS
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approved
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