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 A133766 a(n) = (4*n+1)*(4*n+3)*(4*n+5). 4
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 REFERENCES L. B. W. Jolley, Summation of Series, Dover, 1961. LINKS Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1). FORMULA 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 MAPLE seq((4*n+1)*(4*n+3)*(4*n+5), n=0..40); MATHEMATICA 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 *) PROG (PARI) a(n)=(4*n+1)*(4*n+3)*(4*n+5) \\ Charles R Greathouse IV, Oct 16 2015 CROSSREFS Cf. A001539, A154633. Sequence in context: A105491 A158533 A284070 * A347980 A289951 A112489 Adjacent sequences: A133763 A133764 A133765 * A133767 A133768 A133769 KEYWORD nonn,easy AUTHOR Miklos Kristof, Jan 02 2008 STATUS approved

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Last modified December 7 19:19 EST 2022. Contains 358669 sequences. (Running on oeis4.)