A228141 Numbers that are congruent to {1, 5} mod 20.

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

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