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 A047223 Numbers that are congruent to {1, 2, 3} mod 5. 21
 1, 2, 3, 6, 7, 8, 11, 12, 13, 16, 17, 18, 21, 22, 23, 26, 27, 28, 31, 32, 33, 36, 37, 38, 41, 42, 43, 46, 47, 48, 51, 52, 53, 56, 57, 58, 61, 62, 63, 66, 67, 68, 71, 72, 73, 76, 77, 78, 81, 82, 83, 86, 87, 88, 91, 92, 93, 96, 97, 98, 101, 102, 103, 106, 107 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1). FORMULA G.f.: x*(1+x+x^2+2*x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Oct 08 2011 a(n) = 2*floor((n-1)/3)+n. - Gary Detlefs, Dec 22 2011 From Wesley Ivan Hurt, Jun 14 2016: (Start) a(n) = a(n-1) + a(n-3) - a(n-4) for n>4. a(n) = (15*n-12-6*cos(2*n*Pi/3)+2*sqrt(3)*sin(2*n*Pi/3))/9. a(3k) = 5k-2, a(3k-1) = 5k-3, a(3k-2) = 5k-4. (End) MAPLE A047223:=n->(15*n-12-6*cos(2*n*Pi/3)+2*sqrt(3)*sin(2*n*Pi/3))/9: seq(A047223(n), n=1..100); # Wesley Ivan Hurt, Jun 14 2016 MATHEMATICA Select[Range[100], MemberQ[{1, 2, 3}, Mod[#, 5]]&] (* Harvey P. Dale, Oct 28 2013 *) LinearRecurrence[{1, 0, 1, -1}, {1, 2, 3, 6}, 100] (* Vincenzo Librandi, Jun 15 2016 *) PROG (PARI) a(n)=(n-1)\3*5+n%5 \\ Charles R Greathouse IV, Dec 22 2011 (MAGMA) [n : n in [0..150] | n mod 5 in [1..3]]; // Wesley Ivan Hurt, Jun 14 2016 CROSSREFS Sequence in context: A015841 A175893 A031470 * A004435 A008321 A064472 Adjacent sequences:  A047220 A047221 A047222 * A047224 A047225 A047226 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified March 31 16:44 EDT 2020. Contains 333151 sequences. (Running on oeis4.)