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 A016947 a(n) = (6*n + 3)^3. 4
 27, 729, 3375, 9261, 19683, 35937, 59319, 91125, 132651, 185193, 250047, 328509, 421875, 531441, 658503, 804357, 970299, 1157625, 1367631, 1601613, 1860867, 2146689, 2460375, 2803221, 3176523 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..2000 Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1). FORMULA Sum_{n>=0} 1/a(n) = 7*zeta(3)/216. - Amiram Eldar, Oct 02 2020 a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). - Wesley Ivan Hurt, Oct 02 2020 G.f.: 27*(1+x)*(1+22*x+x^2)/(-1+x)^4. - Wesley Ivan Hurt, Oct 02 2020 EXAMPLE a(0) = (6*0 + 3)^3 = 3^3 = 27. MATHEMATICA Table[(6*n + 3)^3, {n, 0, 25}] (* Amiram Eldar, Oct 02 2020 *) PROG (MAGMA) [(6*n+3)^3: n in [0..50]]; // Vincenzo Librandi, May 05 2011 CROSSREFS Cf. A002117, A016911, A016923, A016935, A016959, A016971. Sequence in context: A097781 A223656 A073537 * A223790 A223976 A167726 Adjacent sequences:  A016944 A016945 A016946 * A016948 A016949 A016950 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified October 25 18:25 EDT 2020. Contains 338012 sequences. (Running on oeis4.)