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 A047253 Numbers that are congruent to {1, 2, 3, 4, 5} mod 6. 19
 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 79, 80, 81, 82, 83, 85, 86 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers that are not divisible by 6. - Benoit Cloitre, Jul 11 2009 More generally the sequence a(n,m) of numbers not divisible by some fixed integer m >= 2 is given by a(n,m) = n - 1 + floor((n+m-2)/(m-1)). - Benoit Cloitre, Jul 11 2009 LINKS Ivan Panchenko, Table of n, a(n) for n = 1..200 Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1). FORMULA a(n) = 5 + a(n-5). G.f.: x*(1+x)*(1+x+x^2)*(x^2-x+1) / ( (x^4+x^3+x^2+x+1)*(x-1)^2 ). a(n) = n - 1 + floor((n+4)/5). - Benoit Cloitre, Jul 11 2009 A122841(a(n)) = 0. - Reinhard Zumkeller, Nov 10 2013 Sum_{n>=1} (-1)^(n+1)/a(n) = (15-4*sqrt(3))*Pi/36. - Amiram Eldar, Dec 31 2021 MATHEMATICA Select[Table[n, {n, 200}], Mod[#, 6]!=0&] (* Vladimir Joseph Stephan Orlovsky, Feb 18 2011*) PROG (PARI) a(n)= 1+n+n\5 (PARI) a(n)=n-1+floor((n+4)/5) \\ Benoit Cloitre, Jul 11 2009 (Haskell) a047253 n = n + n `div` 5 a047253_list = [1..5] ++ map (+ 6) a047253_list -- Reinhard Zumkeller, Nov 10 2013 CROSSREFS Cf. A097325, A122841. Sequence in context: A194386 A187390 A039215 * A248910 A254278 A204878 Adjacent sequences: A047250 A047251 A047252 * A047254 A047255 A047256 KEYWORD nonn,easy AUTHOR N. J. A. Sloane EXTENSIONS Extended by R. J. Mathar, Oct 18 2008 STATUS approved

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Last modified April 16 04:17 EDT 2024. Contains 371696 sequences. (Running on oeis4.)