A050055 a(n) = a(n-1) + a(m) for n >= 4, where m = 2*n - 2 - 2^(p+1) and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = 1, a(2) = 2, and a(3) = 4.

1, 2, 4, 6, 12, 14, 20, 34, 68, 70, 76, 90, 124, 194, 284, 478, 956, 958, 964, 978, 1012, 1082, 1172, 1366, 1844, 2802, 3780, 4862, 6228, 9030, 13892, 22922, 45844, 45846, 45852, 45866, 45900, 45970, 46060, 46254, 46732

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

• Ivan Neretin, Table of n, a(n) for n = 1..8193

Crossrefs

Cf. A050027, A050031, A050035, A050039, A050043, A050047, A050051, A050059, A050063, A050067, A050071 (similar, but with different initial conditions).

Programs

Mathematica

Fold[Append[#1, #1[[-1]] + #1[[#2]]] &, {1, 2, 4}, Flatten@Table[2 k, {n, 5}, {k, 2^n}]] (* Ivan Neretin, Sep 07 2015 *)

PARI

lista(nn) = {nn = max(nn, 3); my(va = vector(nn)); va[1] = 1; va[2] = 2; va[3] = 4; for(n=4, nn, va[n] = va[n-1] + va[2*(n - 1 - 2^logint(n-2, 2))]); va;} \\ Petros Hadjicostas, Jul 19 2020

Extensions

Name edited by Petros Hadjicostas, Jul 19 2020