A050025 a(n) = a(n-1) + a(m) for n >= 4, where m = 2^(p+1) + 2 - n and p is the unique integer such that 2^p < n - 1 <= 2^(p+1), starting with a(1) = a(2) = a(3) = 1.

1, 1, 1, 2, 3, 5, 6, 7, 8, 15, 21, 26, 29, 31, 32, 33, 34, 67, 99, 130, 159, 185, 206, 221, 229, 236, 242, 247, 250, 252, 253, 254, 255, 509, 762, 1014, 1264, 1511, 1753, 1989, 2218, 2439, 2645, 2830, 2989, 3119, 3218, 3285, 3319

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

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

Programs

Maple

a := proc(n) option remember;
`if`(n < 4, 1, a(n - 1) + a(Bits:-Iff(n - 2, n - 2) + 3 - n)); end proc;
seq(a(n), n = 1 .. 48); # Petros Hadjicostas, Nov 08 2019

Mathematica

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

PARI

lista(nn) = {nn = max(nn,3); my(va = vector(nn)); va[1] = 1; va[2] = 1; va[3] = 1; for(n=4, nn, va[n] = va[n-1] + va[2*2^logint(n-2, 2) + 2 - n]); va;} \\ Petros Hadjicostas, May 03 2020

Extensions

Name edited by Petros Hadjicostas, Nov 08 2019