OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..3000 from Ivan Neretin)
EXAMPLE
8 is included because sigma(8) = 15 is relatively prime to sigma(9) = 13.
MATHEMATICA
Select[Range@800, GCD @@ DivisorSigma[1, {#, # + 1}] == 1 &] (* Ivan Neretin, Jan 27 2017 *)
Drop[Position[Partition[DivisorSigma[1, Range[800]], 2, 1], _?(GCD@@#== 1&)]// Flatten, 2] (* Harvey P. Dale, Jul 31 2019 *)
PROG
(PARI) lista(nn) = {for(n=1, nn, if (gcd(sigma(n), sigma(n+1)) == 1, print1(n, ", "))); } \\ Michel Marcus, May 19 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Nov 11 2000
STATUS
approved