A369490 a(n) = 3^(n+1) + 2*(-2)^(n+1).

-1, 17, 11, 113, 179, 857, 1931, 7073, 18659, 61097, 173051, 539633, 1577939, 4815737, 14283371, 43177793, 128878019, 387944777, 1161212891, 3488881553, 10456158899, 31389448217, 94126401611, 282463090913, 847221500579, 2542000046057

Offset: 0

Author

Philippe Deléham, Jan 24 2024

Keywords

• sign
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (1, 6).

Crossrefs

Cf. A000079, A000244, A003063, A015441, A085279.

Programs

Mathematica

LinearRecurrence[{1,6},{-1,17},26] (* James C. McMahon, Jan 30 2024 *)

Python

def A369490(n): return 3**(n+1)+(1<Chai Wah Wu, Feb 25 2024

Formula

a(n) = a(n-1) + 6*a(n-2); a(0) = -1, a(1) = 17.

G.f.: (18*x-1)/((1+2*x)*(1-3*x)).

a(2*n) = A003063(2*n+2).

a(2*n+1) = A085279(2*n+3).

a(n) = 18*A015441(n) - A015441(n+1).