OFFSET
1,1
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..10000
MATHEMATICA
mx = 100; Complement[Range[mx], Table[Nest[DivisorSigma[1, #] &, n, 2], {n, mx}]] (* Ivan Neretin, Feb 12 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jul 17 2009
STATUS
approved