OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
MATHEMATICA
nonPrime[n_Integer] := FixedPoint[n + PrimePi@# &, n + PrimePi@n];
A087156[n_] := Mod[n, DivisorSigma[1, n]]; A141468 := Array[nonPrime, 60, 0]; Table[2*A087156[n] - A141468[[n]], {n, 1, 50}] (* G. C. Greubel, Aug 02 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Aug 03 2009
EXTENSIONS
Entries checked by R. J. Mathar, May 21 2010
STATUS
approved