A106387 Numbers j such that 6j^2 + 6j + 1 = 11k.

4, 6, 15, 17, 26, 28, 37, 39, 48, 50, 59, 61, 70, 72, 81, 83, 92, 94, 103, 105, 114, 116, 125, 127, 136, 138, 147, 149, 158, 160, 169, 171, 180, 182, 191, 193, 202, 204, 213, 215, 224, 226, 235, 237, 246, 248, 257, 259, 268, 270, 279, 281, 290, 292, 301, 303

Offset

1,1

Comments

k sequence = A106388.

Links

Table of n, a(n) for n=1..56.

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

Formula

j(1)=4, j(2)=6 then j(n)=j(n-2)+11.

a(n) = 11*n - a(n-1) - 12 (with a(1)=4). - Vincenzo Librandi, Nov 13 2010

a(2k-1) = 11k - 7, a(2k) = 11k - 5. - Ralf Stephan, Nov 15 2010

From Bruno Berselli, Nov 16 2010: (Start)

a(n) = (22*n - 7*(-1)^n - 13)/4.

G.f.: x*(4+2*x+5*x^2)/((1+x)*(1-x)^2).

a(n) - a(n-1) - a(n-2) + a(n-3) = 0 for n > 3.

a(n) - a(n-2) = 11 for n > 2.

a(n) - 2*a(n-1) + a(n-2) = -7*(-1)^n for n > 2. (End)

Mathematica

Select[Range[320], Divisible[6#^2+6#+1, 11]&] (* Harvey P. Dale, Sep 10 2011 *)

Prog

(PARI) Vec((4+2*x+5*x^2)/(1+x)/(1-x)^2+O(x^99)) \\ Charles R Greathouse IV, Dec 28 2011

Crossrefs

Cf. A106388, A106389, A106390.

Sequence in context: A055719 A349157 A117883 * A034771 A294457 A266883

Adjacent sequences: A106384 A106385 A106386 * A106388 A106389 A106390

Keyword

nonn,easy

Author

Pierre CAMI, May 01 2005

Status

approved