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 A013726 a(n) = 21^(2*n + 1). 3
 21, 9261, 4084101, 1801088541, 794280046581, 350277500542221, 154472377739119461, 68122318582951682301, 30041942495081691894741, 13248496640331026125580781, 5842587018385982521381124421 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (441). FORMULA From Philippe Deléham, Nov 28 2008: (Start) a(n) = 441*a(n-1); a(0)=21. G.f.: 21/(1-441*x). (End) a(n) = A009965(A005408(n)). - Wesley Ivan Hurt, Feb 10 2014 MAPLE seq(21^(2*n+1), n=0..10); # Nathaniel Johnston, Jun 25 2011 MATHEMATICA Table[21^(2 n + 1), {n, 0, 15}] (* Wesley Ivan Hurt, Feb 10 2014 *) PROG (MAGMA) [21^(2*n+1): n in [0..15]]; // Vincenzo Librandi, Jun 26 2011 (PARI) a(n)=21^(2*n+1) \\ Charles R Greathouse IV, Jul 11 2016 CROSSREFS Bisection of A009965 (21^n). Cf. A013708-A013725, A013727-A013729. Sequence in context: A263278 A176446 A135823 * A159358 A048914 A046183 Adjacent sequences:  A013723 A013724 A013725 * A013727 A013728 A013729 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified November 13 17:50 EST 2018. Contains 317149 sequences. (Running on oeis4.)