A113802 - OEIS

A113802

Numbers that are congruent to {2, 12} mod 14.

2, 12, 16, 26, 30, 40, 44, 54, 58, 68, 72, 82, 86, 96, 100, 110, 114, 124, 128, 138, 142, 152, 156, 166, 170, 180, 184, 194, 198, 208, 212, 222, 226, 236, 240, 250, 254, 264, 268, 278, 282, 292, 296, 306, 310, 320, 324, 334, 338, 348, 352, 362, 366, 376, 380

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

FORMULA

a(n) = 14*n - a(n-1) - 14 (with a(1) = 2). - Vincenzo Librandi, Nov 13 2010

From Wolfdieter Lang, Dec 15 2011: (Start)

a(n) = 7*n-(7-3*(-1)^n)/2.

O.g.f.: 2*x*(1+5*x+x^2)/((1+x)*(1-x)^2).

See the contribution of Bruno Berselli under A113801. (End)

Sum_{n>=1} (-1)^(n+1)/a(n) = cot(Pi/7)*Pi/14. - Amiram Eldar, Dec 30 2021