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 A213967 a(n)=n for n<=3; thereafter a(n)=a(n-1)+a(n-2)+a(n-3)+1. 3
 0, 1, 2, 3, 7, 13, 24, 45, 83, 153, 282, 519, 955, 1757, 3232, 5945, 10935, 20113, 36994, 68043, 125151, 230189, 423384, 778725, 1432299, 2634409, 4845434, 8912143, 16391987, 30149565, 55453696, 101995249, 187598511, 345047457, 634641218, 1167287187 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES Atanassov, K. T.; Atanassova, V.; Shannon, A. G.; Turner, J. C. New visual perspectives on Fibonacci numbers. With a foreword by A. F. Horadam. World Scientific Publishing Co., Inc., River Edge, NJ, 2002. xvi+313 pp. ISBN: 981-238-134-1 MR1932564 (2003h:11015). See p. 68. LINKS Bruno Berselli, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (2,0,0,-1). FORMULA G.f.: x*(1-x^2+x^3)/(1-2*x+x^4). - Bruno Berselli, Jul 02 2012 MAPLE f:=proc(n) option remember; if n <= 3 then n else f(n-1)+f(n-2)+f(n-3)+1; fi; end: seq(f(n), n=0..60); MATHEMATICA Join[{0}, LinearRecurrence[{2, 0, 0, -1}, {1, 2, 3, 7}, 40]] (* Jean-François Alcover, Feb 13 2018 *) PROG (MAGMA) [n le 3 select n else Self(n)+Self(n-1)+Self(n-2)+1: n in [0..35]]; // Bruno Berselli, Jul 02 2012 (Haskell) a213967 n = a213967_list !! n a213967_list = 0 : xs where                xs = 1 : 2 : 3 : map (+ 1)                     (zipWith3 (((+) .) . (+)) xs (tail xs) (drop 2 xs)) -- Reinhard Zumkeller, Dec 29 2014 CROSSREFS Cf. A001590. Cf. A248098. Sequence in context: A330028 A075058 A213968 * A128695 A024504 A256494 Adjacent sequences:  A213964 A213965 A213966 * A213968 A213969 A213970 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jun 30 2012 STATUS approved

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Last modified August 5 06:46 EDT 2020. Contains 336209 sequences. (Running on oeis4.)