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 A005688 Numbers of Twopins positions. (Formerly M0647) 1
 1, 2, 3, 5, 7, 10, 14, 20, 30, 45, 69, 104, 157, 236, 356, 540, 821, 1252, 1908, 2909, 4434, 6762, 10319, 15755, 24066, 36766, 56176, 85837, 131172, 200471, 306410, 468371, 715975, 1094516, 1673232, 2557997, 3910683 (list; graph; refs; listen; history; text; internal format)
 OFFSET 5,2 COMMENTS The complete sequence by R. K. Guy in "Anyone for Twopins?" starts with a(0) = 0, a(1) = 1, a(2) = 1, a(3) = 1 and a(4) =1. The formula for a(n) confirms these values. - Johannes W. Meijer, Aug 24 2013 REFERENCES R. K. Guy, ``Anyone for Twopins?,'' in D. A. Klarner, editor, The Mathematical Gardner. Prindle, Weber and Schmidt, Boston, 1981, pp. 2-15. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. K. Guy, Anyone for Twopins?, in D. A. Klarner, editor, The Mathematical Gardner. Prindle, Weber and Schmidt, Boston, 1981, pp. 2-15. [Annotated scanned copy, with permission] Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1,2,-2,0,0,0,-1). FORMULA G.f.: (x^5*(1-x^2+x^3-2*x^5-x^6-x^7-x^8-x^9))/((1-x^2-x^5)*(1-2*x+x^2-x^5)). - Ralf Stephan, Apr 22 2004 a(n) = sum(A102541(n-k-1, 2*k), k=0..floor((n-1)/3)), n >= 5. - Johannes W. Meijer, Aug 24 2013 MATHEMATICA LinearRecurrence[{2, 0, -2, 1, 2, -2, 0, 0, 0, -1}, {1, 2, 3, 5, 7, 10, 14, 20, 30, 45}, 40] (* Harvey P. Dale, Aug 26 2019 *) CROSSREFS Sequence in context: A094984 A107332 A002062 * A241550 A319564 A221943 Adjacent sequences:  A005685 A005686 A005687 * A005689 A005690 A005691 KEYWORD nonn,easy AUTHOR EXTENSIONS More terms from Johannes W. Meijer, Aug 24 2013 STATUS approved

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Last modified June 5 18:48 EDT 2020. Contains 334854 sequences. (Running on oeis4.)