A047276 Numbers that are congruent to {2, 6} mod 7.

2, 6, 9, 13, 16, 20, 23, 27, 30, 34, 37, 41, 44, 48, 51, 55, 58, 62, 65, 69, 72, 76, 79, 83, 86, 90, 93, 97, 100, 104, 107, 111, 114, 118, 121, 125, 128, 132, 135, 139, 142, 146, 149, 153, 156, 160, 163, 167, 170, 174, 177, 181, 184, 188, 191, 195, 198, 202, 205

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
• Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

Programs

Mathematica

Table[3*n + Floor[n/2] - 1, {n, 100}] (* Paolo Xausa, Sep 02 2024 *)

PARI

a(n) = 3*n + floor(n/2) - 1 \\ David Lovler, Sep 12 2022

Formula

a(n) = 7*n - a(n-1) - 6 (with a(1)=2). - Vincenzo Librandi, Aug 05 2010

G.f.: x*(2 + 4*x + x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Oct 25 2011

a(n) = 3*n + floor(n/2) - 1. - Arkadiusz Wesolowski, Sep 19 2012

E.g.f.: 1 + ((14*x - 5)*exp(x) + exp(-x))/4. - David Lovler, Sep 12 2022