A049948 - OEIS

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A049948

a(n) = a(1) + a(2) + ... + a(n-1) + a(m) for n >= 4, where m = 2*n - 3 - 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) = 1.

1, 2, 1, 5, 10, 20, 40, 89, 208, 377, 754, 1517, 3064, 6296, 13138, 28586, 67246, 121355, 242710, 485429, 970888, 1941944, 3884434, 7771178, 15552430, 31158968, 62493400, 125714978, 254343502, 520355000, 1087650970, 2367152042

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..32.

MAPLE

s := proc(n) option remember; `if`(n < 1, 0, a(n) + s(n - 1)) end proc:

a := proc(n) option remember;

`if`(n < 4, [1, 2, 1][n], s(n - 1) + a(-2^ceil(log[2](n - 1)) + 2*n - 3)):

end proc:

seq(a(n), n = 1..40); # Petros Hadjicostas, Nov 15 2019

CROSSREFS