1,2

Table of n, a(n) for n=1..71.

a(n)=A002808(n)-A000005(A002808(n)) = A002808(n)-A035004(n+1).

a(1)=4-3=1, a(2)=6-4=2, a(3)=8-4=4.

With[{comps=Rest[Complement[Range[100], Prime[Range[PrimePi[100]]]]]}, #-DivisorSigma[0, #]&/@comps] (* Harvey P. Dale, Dec 16 2011 *)

Cf. A000005, A002808.

Sequence in context: A050825 A174342 A111150 * A078611 A211376 A278249

Adjacent sequences: A166980 A166981 A166982 * A166984 A166985 A166986

nonn

Juri-Stepan Gerasimov, Oct 26 2009

Formula and two entries corrected by R. J. Mathar, May 21 2010.

approved