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 A007486 a(n) = a(n-1) + a(n-2) + a(n-3). (Formerly M2351) 1
 1, 3, 4, 8, 15, 27, 50, 92, 169, 311, 572, 1052, 1935, 3559, 6546, 12040, 22145, 40731, 74916, 137792, 253439, 466147, 857378, 1576964, 2900489, 5334831, 9812284, 18047604, 33194719, 61054607, 112296930, 206546256, 379897793, 698740979, 1285185028 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS If A001590 is the tribonacci sequence, this might be called the Trucas sequence after the Lucas sequence A000032. - Paul Wayper (paulway(AT)mabula.net), Nov 28 2007 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence) LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Martin Burtscher, Igor Szczyrba, RafaĆ Szczyrba, Analytic Representations of the n-anacci Constants and Generalizations Thereof, Journal of Integer Sequences, Vol. 18 (2015), Article 15.4.5. N. G. Voll, Some identities for four term recurrence relations, Fib. Quart., 51 (2013), 268-273. Index entries for linear recurrences with constant coefficients, signature (1,1,1). FORMULA O.g.f.: x*(1+2*x)/(1-x-x^2-x^3). a(n) = A001590(n)+3*A000073(n). - R. J. Mathar, Aug 22 2008 a(n) = 2*a(n-1) - a(n-4), n>4. - Vincenzo Librandi, Jun 08 2011 MATHEMATICA LinearRecurrence[{1, 1, 1}, {1, 3, 4}, 100] (* Vladimir Joseph Stephan Orlovsky, Jun 07 2011 *) CoefficientList[Series[(1 + 2 x) / (1 - x - x^2 - x^3), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 09 2013 *) PROG (PARI) Vec((x+2*x^2)/(1-x-x^2-x^3)+O(x^99)) \\ Charles R Greathouse IV, Jun 08 2011 (MAGMA) I:=[1, 3, 4]; [n le 3 select I[n] else Self(n-1)+Self(n-2)+Self(n-3): n in [1..50]]; // Vincenzo Librandi, Jun 09 2013 CROSSREFS Cf. A001590, A000032, A000045. Sequence in context: A310013 A033854 A042981 * A027977 A165438 A293781 Adjacent sequences:  A007483 A007484 A007485 * A007487 A007488 A007489 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified August 8 02:41 EDT 2020. Contains 336290 sequences. (Running on oeis4.)