OFFSET
1,3
COMMENTS
Note that the quotient obtained when sigma(k) divides k*(k+1)/2 with k = A076617(n) is a(n) + 1.
EXAMPLE
A076617(6) = 95; sigma(95) = 120 and antisigma(95) = 4440, hence a(6) = 4440 / 120 = 37.
MATHEMATICA
Select[Table[(k*(k + 1)/2)/DivisorSigma[1, k] - 1, {k, 1, 10^6}], IntegerQ] (* Amiram Eldar, Apr 14 2022 *)
PROG
(PARI) is(n) = n*(n+1)/2%sigma(n) == 0; \\ A076617
f(n) = n*(n+1)/(2*sigma(n)) - 1;
lista(nn) = apply(f, select(is, [1..nn])); \\ Michel Marcus, Apr 15 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Bernard Schott, Apr 14 2022
EXTENSIONS
More terms from Amiram Eldar, Apr 14 2022
STATUS
approved