OFFSET
1,2
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
EXAMPLE
The divisors of 56 are 1, 2, 4, 7, 8, 14, 28, 56, so tau(56) = 8 and sigma(56) = 120. As gcd(56, 120) = tau(56) = 8, so 56 belongs to this sequence. - Bernard Schott, Oct 18 2019
MATHEMATICA
Select[Range[2500], GCD[DivisorSigma[1, #], #] == DivisorSigma[0, #] &] (* Jayanta Basu, Mar 21 2013 *)
PROG
(PARI) for(n=1, 3000, if(gcd(n, sigma(n))==numdiv(n), print1(n, ", ")))
(Magma) [k:k in [1..2300]| Gcd(k, DivisorSigma(1, k)) eq #Divisors(k)]; // Marius A. Burtea, Oct 18 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 30 2002
STATUS
approved