A120135 a(n) = 5 + floor((1 + Sum_{j=1..n-1} a(j)) / 2).

5, 8, 12, 18, 27, 40, 60, 90, 135, 203, 304, 456, 684, 1026, 1539, 2309, 3463, 5195, 7792, 11688, 17532, 26298, 39447, 59171, 88756, 133134, 199701, 299552, 449328, 673992, 1010988, 1516482, 2274723, 3412084, 5118126, 7677189, 11515784

Offset: 1

Author

Graeme McRae, Jun 10 2006

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A073941, A072493, A112088, A120134, A120136 - A120209.

Programs

Mathematica

a[n_]:= a[n]= 5 +Floor[(1+Sum[a[k], {k,n-1}])/2];
Table[a[n], {n,60}] (* G. C. Greubel, May 07 2023 *)

SageMath

@CachedFunction
def A120135(n): return 5 + (1 + sum(A120135(k) for k in range(1,n)))//2
[A120135(n) for n in range(1,61)] # G. C. Greubel, May 07 2023

Formula

a(n) ~ c * (3/2)^n, where c = 3.514931952760438754899508881646642282344325354834703833076259269449577... - Vaclav Kotesovec, May 07 2023