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 A232713 Doubly pentagonal numbers: a(n) = n*(3*n-2)*(3*n-1)*(3*n+1)/8. 9
 0, 1, 35, 210, 715, 1820, 3876, 7315, 12650, 20475, 31465, 46376, 66045, 91390, 123410, 163185, 211876, 270725, 341055, 424270, 521855, 635376, 766480, 916895, 1088430, 1282975, 1502501, 1749060, 2024785, 2331890, 2672670, 3049501, 3464840, 3921225, 4421275 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Bruno Berselli, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1). FORMULA G.f.: x*(1 + 30*x + 45*x^2 + 5*x^3) / (1 - x)^5. a(n) = A000326(A000326(n)) = A000332(3n+1). MATHEMATICA Table[n (3 n - 2) (3 n - 1) (3 n + 1)/8, {n, 0, 40}] PROG (MAGMA) [n*(3*n-2)*(3*n-1)*(3*n+1)/8: n in [0..40]]; (PARI) a(n)=n*(3*n-2)*(3*n-1)*(3*n+1)/8 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Cf. A000326, A000332. Cf. similar sequences: A000583 for A000290(A000290(n)); A002817 for A000217(A000217(n)); A063249 for A000384(A000384(n)). Cf. A236770, A260810. Sequence in context: A219831 A184200 A219942 * A007329 A101628 A064013 Adjacent sequences:  A232710 A232711 A232712 * A232714 A232715 A232716 KEYWORD nonn,easy AUTHOR Bruno Berselli, Nov 28 2013 STATUS approved

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Last modified October 20 15:29 EDT 2019. Contains 328267 sequences. (Running on oeis4.)