A049947 - OEIS

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A049947

a(n) = a(1) + a(2) + ... + 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(3) = 4.

1, 1, 4, 7, 20, 34, 74, 175, 491, 808, 1622, 3271, 6683, 13999, 30461, 71650, 200951, 330253, 660512, 1321051, 2642243, 5285119, 10572701, 21156130, 42369911, 84998425, 170987648, 345939364, 707749739, 1479341773, 3219624485

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Table of n, a(n) for n=1..31.

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

end proc:

seq(a(n), n = 1..40); # Petros Hadjicostas, Apr 25 2020

CROSSREFS