A198643 a(n) = 5*3^n-1.

4, 14, 44, 134, 404, 1214, 3644, 10934, 32804, 98414, 295244, 885734, 2657204, 7971614, 23914844, 71744534, 215233604, 645700814, 1937102444, 5811307334, 17433922004, 52301766014, 156905298044, 470715894134, 1412147682404, 4236443047214

Offset: 0

Author

Vincenzo Librandi, Oct 28 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Amya Luo, Pattern Avoidance in Nonnesting Permutations, Undergraduate Thesis, Dartmouth College (2024). See p. 11.
• Index entries for linear recurrences with constant coefficients, signature (4,-3).

Crossrefs

Cf. A027107, A048473, A171498.

Programs

Magma

[5*3^n-1: n in [0..30]];

Mathematica

5*3^Range[0, 30] - 1 (* or *)
NestList[3*# + 2 &, 4, 30] (* Paolo Xausa, Aug 28 2024 *)

PARI

a(n)=5*3^n-1 \\ Charles R Greathouse IV, Oct 07 2015

Formula

a(n) = 3*a(n-1)+2 = 2*A060816(n+1).

G.f.: ( 4-2*x ) / ( (3*x-1)*(x-1) ). - R. J. Mathar, Nov 17 2011