A050039 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) = a(2) = 1 and a(2) = 4.

1, 1, 4, 5, 10, 11, 16, 27, 54, 55, 60, 71, 98, 153, 224, 377, 754, 755, 760, 771, 798, 853, 924, 1077, 1454, 2209, 2980, 3833, 4910, 7119, 10952, 18071, 36142, 36143, 36148, 36159, 36186, 36241, 36312, 36465, 36842, 37597, 38368

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

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

Crossrefs

Cf. A050027, A050031, A050035, A050043, A050047, A050051, A050055, A050059, A050063, A050067, A050071 (similar, but with different initial conditions).

Programs

Mathematica

Fold[Append[#1, #1[[-1]] + #1[[#2]]] &, {1, 1, 4}, Flatten@Table[2 k, {n, 5}, {k, 2^n}]] (* Ivan Neretin, Sep 06 2015 *)

PARI

lista(nn) = {nn = max(nn, 3); my(va = vector(nn)); va[1] = 1; va[2] = 1; va[3] = 4; for(n=4, nn, va[n] = va[n-1] + va[2*(n - 1 - 2^logint(n-2, 2))]); va; } \\ Petros Hadjicostas, May 15 2020

Extensions

Name edited by Petros Hadjicostas, May 15 2020