0,1

It is easy to verify the first three terms using sequences A000005, A000203, and A001157. The first term of A131908 gives a(3). The a(4) term is greater than 10^8. Does a(n) exist for all n?

Table of n, a(n) for n=0..3.

sigma_0(2)=sigma_0(3); sigma_1(6)=sigma_1(12); sigma_2(6)=sigma_2(7); sigma_3(184926)=sigma_3(194315).

Sequence in context: A279841 A219195 A212223 * A257478 A243523 A011044

Adjacent sequences: A158912 A158913 A158914 * A158916 A158917 A158918

more,nonn

T. D. Noe, Mar 30 2009

approved