0,3

Inverse of the Jacobsthal sequence (A001045), nearly, since a(A001045(n))=n except for n=2 (see A130249 for another version). a(n+1) is equal to the partial sum of the Jacobsthal indicator sequence (see A105348).

Table of n, a(n) for n=0..100.

a(n) = ceiling(log_2(3n-1)) = 1 + floor(log_2(3n-2)) for n >= 1.

a(n) = A130249(n-1) + 1 = A130253(n-1) for n >= 1.

G.f.: g(x) = (x/(1-x))*Sum_{k>=0} x^A001045(k).

a(10)=5 because A001045(5) = 11 >= 10, but A001045(4) = 5 < 10.

For partial sums see A130252.

Other related sequences A130249, A130253, A105348. A001045, A130234, A130242.

Sequence in context: A021303 A303821 A240622 * A130253 A145288 A075324

Adjacent sequences: A130247 A130248 A130249 * A130251 A130252 A130253

nonn

Hieronymus Fischer, May 20 2007

approved