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 A017101 a(n) = 8n + 3. 23
 3, 11, 19, 27, 35, 43, 51, 59, 67, 75, 83, 91, 99, 107, 115, 123, 131, 139, 147, 155, 163, 171, 179, 187, 195, 203, 211, 219, 227, 235, 243, 251, 259, 267, 275, 283, 291, 299, 307, 315, 323, 331, 339, 347, 355, 363, 371, 379, 387, 395, 403, 411, 419, 427 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Apart from initial term(s), dimension of the space of weight 2n cusp forms for Gamma_0( 47 ). Also numbers of the form x^2 + y^2 + z^2, where x,y,z are odd integers. - Alexander Adamchuk, Dec 01 2006 2*a(n) is the half-period of oscillation of a Langton's ant colony that is n basic blocks in length. To construct such blocks use a pair of ants facing north at (x,y) and (x+1,y+2) (using Golly's coordinate system). Each successive block is placed 1 cell away from the previous one, i.e., the x coordinate shifts by 3, so we have (x+3k,y) and (x+3k+1,y+2). Also, because of the symmetry of the oscillation pattern, 4*a(n) is the length of the whole period. - Mikhail Kurkov, Nov 20 2019 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..5000 Tanya Khovanova, Recursive Sequences MathOverflow, Absolute oscillator in Langton's ant William A. Stein, Dimensions of the spaces S_k(Gamma_0(N)) William A. Stein, The modular forms database Index entries for linear recurrences with constant coefficients, signature (2,-1). FORMULA a(n) = A001969(2*n+1) + A001969(2*n) = A000069(2*n+1) + A000069(2*n). - Philippe Deléham, Feb 04 2004 G.f.: (3+5*x)/(1-x)^2. - R. J. Mathar, Mar 30 2011 a(n) = 2*a(n-1) - a(n-2) for n>1. - Vincenzo Librandi, May 28 2011 a(A002265(n)) = A004442(n) + A004443(n). - Wesley Ivan Hurt, Apr 06 2016 E.g.f.: exp(x)*(3 + 8*x). - Stefano Spezia, Nov 20 2019 MAPLE A017101:=n->8*n+3: seq(A017101(n), n=0..100); # Wesley Ivan Hurt, Apr 06 2016 MATHEMATICA Range[3, 1000, 8] (* Vladimir Joseph Stephan Orlovsky, May 27 2011 *) PROG (MAGMA) [8*n+3: n in [0..60]]; // Vincenzo Librandi, May 28 2011 (PARI) a(n)=8*n+3 \\ Charles R Greathouse IV, Jun 02 2013 CROSSREFS Cf. A000069, A001969, A002265, A004442, A004443, A004769, A017077, A017089. Sequence in context: A113295 A043433 A078583 * A112422 A289840 A125994 Adjacent sequences:  A017098 A017099 A017100 * A017102 A017103 A017104 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified August 3 13:49 EDT 2020. Contains 336198 sequences. (Running on oeis4.)