OFFSET
1,2
COMMENTS
Also, 1 together with the numbers A073255.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MAPLE
with(NumberTheory): seq(`if`(isprime(n), NULL, sigma(n)), n = 1 .. 100); # Reza K Ghazi, Aug 28 2021
MATHEMATICA
Join[{1}, DivisorSigma[1, #]&/@Select[Range[100], CompositeQ]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 27 2017 *)
PROG
(PARI) a = List(); for(n=1, 100, if(!isprime(n), listput(a, sigma(n)))); Vec(a) \\ Reza K Ghazi, Aug 28 2021
(SageMath) [sigma(n) for n in range(1, 101) if not is_prime(n)] # Reza K Ghazi Aug 28 2021
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Jul 04 2009
STATUS
approved