OFFSET
1,2
COMMENTS
a(30) > 10^9.
EXAMPLE
a(2) = 6 because gcd(sigma(1), 1) = 1, gcd(sigma(2), 2) = 1, gcd(sigma(3), 3) = 1, gcd(sigma(4), 4) = 1, gcd(sigma(5), 5) = 1, and for n = 6, we have gcd(sigma(6), 6) = 6, which is greater than the five preceding.
PROG
(PARI) mgcdab(n) = { m = 0; for (i=1, n, g = gcd(sigma(i), i); if (g > m, m = g; print1(i, ", "); ); ); }
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Sep 16 2012
EXTENSIONS
a(30)-a(32) from Donovan Johnson, Sep 17 2012
STATUS
approved