cp's OEIS Frontend

A049901 a(n) = a(1) + a(2) + ... + 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) = 1, a(2) = 2, and a(3) = 1.

%I A049901 #13 Nov 16 2019 03:29:53
%S A049901 1,2,1,2,5,9,19,37,75,114,246,502,1008,2019,4039,8077,16155,24234,
%T A049901 52506,107032,215075,430656,861568,1723268,3446575,6893188,13786394,
%U A049901 27572798,55145600,110291203,220582407,441164813,882329627,1323494442
%N A049901 a(n) = a(1) + a(2) + ... + 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) = 1, a(2) = 2, and a(3) = 1.
%p A049901 s := proc(n) option remember; `if`(n < 1, 0, a(n) + s(n - 1)) end proc:
%p A049901 a := proc(n) option remember;
%p A049901 `if`(n < 4, [1, 2, 1][n], s(n - 1) - a(2^ceil(log[2](n - 1)) + 2 - n)):
%p A049901 end proc:
%p A049901 seq(a(n), n = 1..40); # _Petros Hadjicostas_, Nov 14 2019
%Y A049901 Cf. A049885, A049893, A049913, A049917, A049921.
%K A049901 nonn
%O A049901 1,2
%A A049901 _Clark Kimberling_
%E A049901 Name edited by _Petros Hadjicostas_, Nov 14 2019