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 A151979 Numbers congruent to {0, 1} mod 19. 4
 0, 1, 19, 20, 38, 39, 57, 58, 76, 77, 95, 96, 114, 115, 133, 134, 152, 153, 171, 172, 190, 191, 209, 210, 228, 229, 247, 248, 266, 267, 285, 286, 304, 305, 323, 324, 342, 343, 361, 362, 380, 381, 399, 400, 418, 419, 437, 438, 456, 457, 475, 476, 494, 495, 513, 514, 532 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Numbers n such that n^2 - n is divisible by 19. LINKS Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA a(n+1) = Sum_k>=0 {A030308(n,k)*b(k)} with b(0)=1 and b(k)=19*2^(k-1) for k>0. - Philippe Deléham, Oct 19 2011 G.f.: x^2*(1+18*x)/((1-x)^2*(1+x)). - Colin Barker, Apr 09 2012 a(n) = a(n-1)+a(n-2)-a(n-3). - Colin Barker, Apr 09 2012 From Stefano Spezia, Feb 01 2020: (Start) a(n) = (1/4)*(38*n - 55 - 17*(-1)^n). E.g.f.: (19/2)*(x*(cosh(x) + sinh(x)) - sinh(x)) - 18*(cosh(x) - 1). (End) MATHEMATICA Select[Range[0, 600], MemberQ[{0, 1}, Mod[#, 19]]&] (* Harvey P. Dale, Feb 11 2019 *) PROG (MAGMA) [n : n in [0..600] | n mod 19 in [0, 1]]; // Vincenzo Librandi, Feb 04 2020 CROSSREFS Sequence in context: A274340 A241849 A054304 * A022109 A041730 A041732 Adjacent sequences:  A151976 A151977 A151978 * A151980 A151981 A151982 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Aug 23 2009 STATUS approved

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Last modified May 27 18:56 EDT 2020. Contains 334664 sequences. (Running on oeis4.)