OFFSET
2,1
COMMENTS
Diagonal of triangle is A020639. - Michel Marcus, Aug 29 2013
LINKS
Diana Mecum, Table of n, a(n) for n=2,...,4951
FORMULA
If gcd(m,n) = 1 then T(m,n) = smallest prime factor of m times smallest prime factor of n, if gcd(m,n) > 1 then T(m,n) = min { smallest prime factor of m times smallest prime factor of n, smallest prime factor of gcd(m,n) }.
EXAMPLE
Triangle begins:
2
6 3
2 6 2
10 15 10 5
2 3 2 10 2
...
PROG
(PARI) t(m, n) = {ff = factor(m)[1, 1] * factor(n)[1, 1]; if ((g = gcd(m, n)) == 1, t = ff, t = min(ff, factor(g)[1, 1]); ); t; } - Michel Marcus, Aug 29 2013
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
N. J. A. Sloane, Dec 28 2008, based on emails from Leroy Quet and Diana Mecum
STATUS
approved