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 A003522 a(n) = Sum_{k=0..n} C(n-k,3k). (Formerly M1391) 5
 1, 1, 1, 1, 2, 5, 11, 21, 37, 64, 113, 205, 377, 693, 1266, 2301, 4175, 7581, 13785, 25088, 45665, 83097, 151169, 274969, 500162, 909845, 1655187, 3011157, 5477917, 9965312, 18128529, 32978725, 59993817, 109139117, 198543154 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 REFERENCES A. Brousseau, Fibonacci and Related Number Theoretic Tables. Fibonacci Association, San Jose, CA, 1972, p. 113. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS V. C. Harris, C. C. Styles, A generalization of Fibonacci numbers, Fib. Quart. 2 (1964) 277-289, sequence u(n,1,3). V. E. Hoggatt, Jr., 7-page typed letter to N. J. A. Sloane with suggestions for new sequences, circa 1977. Vedran Krcadinac, A new generalization of the golden ratio, Fibonacci Quart. 44 (2006), no. 4, 335-340. Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992. Simon Plouffe, 1031 Generating Functions and Conjectures, Université du Québec à Montréal, 1992. Index entries for linear recurrences with constant coefficients, signature (3, -3, 1, 1). FORMULA G.f. : (1-x)^2/(1-3x+3x^2-x^3-x^4); a(n)=3a(n-1)-3a(n-2)+a(n-3)+a(n-4). - Paul Barry, Jul 07 2004 MAPLE A003522:=-(z-1)**2/(-1+3*z-3*z**2+z**4+z**3); # conjectured by Simon Plouffe in his 1992 dissertation MATHEMATICA LinearRecurrence[{3, -3, 1, 1}, {1, 1, 1, 1}, 35] (* Ray Chandler, Sep 23 2015 *) PROG (PARI) a(n)=if(n<0, 0, polcoeff((1-x)^2/(1-3*x+3*x^2-x^3-x^4)+x*O(x^n), n)) /* Michael Somos, Sep 20 2005 */ CROSSREFS Sequence in context: A137356 A103198 A183929 * A112805 A119970 A082775 Adjacent sequences:  A003519 A003520 A003521 * A003523 A003524 A003525 KEYWORD nonn AUTHOR STATUS approved

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Last modified October 20 07:17 EDT 2018. Contains 316378 sequences. (Running on oeis4.)