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A049912
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) = 4.
0
1, 2, 4, 6, 9, 21, 39, 73, 116, 270, 537, 1069, 2108, 4139, 7857, 14143, 22537, 52930, 105857, 211709, 423388, 846699, 1692977, 3384383, 6763017, 13511354, 26939388, 53561245, 105852901, 206635762, 393095153, 707276793, 1127311334
OFFSET
1,2
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, 4][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
Sequence in context: A192079 A079143 A192316 * A268868 A271927 A227526
KEYWORD
nonn
EXTENSIONS
Name edited by Petros Hadjicostas, Nov 15 2019
STATUS
approved