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 A228141 Numbers that are congruent to {1, 5} mod 20. 2
 1, 5, 21, 25, 41, 45, 61, 65, 81, 85, 101, 105, 121, 125, 141, 145, 161, 165, 181, 185, 201, 205, 221, 225, 241, 245, 261, 265, 281, 285, 301, 305, 321, 325, 341, 345, 361, 365, 381, 385, 401, 405, 421, 425, 441, 445, 461, 465, 481, 485, 501, 505, 521, 525 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Colin Barker, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA a(n) = -3*(4+(-1)^n) + 10*n. a(n) = a(n-1) + a(n-2) - a(n-3). G.f.: x*(15*x^2+4*x+1) / ((x-1)^2*(x+1)). E.g.f.: 15 + (10*x - 12)*exp(x) - 3*exp(-x). - David Lovler, Sep 05 2022 MATHEMATICA Flatten[Table[20n + {1, 5}, {n, 0, 24}]] (* Alonso del Arte, Aug 12 2013 *) PROG (PARI) Vec(x*(15*x^2+4*x+1)/((x-1)^2*(x+1)) + O(x^100)) CROSSREFS Cf. A216815, A216816, A228142. Sequence in context: A113410 A099654 A195959 * A268527 A176300 A042319 Adjacent sequences: A228138 A228139 A228140 * A228142 A228143 A228144 KEYWORD nonn,easy AUTHOR Colin Barker, Aug 12 2013 STATUS approved

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Last modified September 11 23:02 EDT 2024. Contains 375842 sequences. (Running on oeis4.)