OFFSET

1,1

COMMENTS

An abc-hit is a triple of coprime positive integers a, b, c such that a + b = c and rad(abc) < c, where rad(n) is the largest squarefree number dividing n.

Conjecture: a(n) > 0 for all n. - Jianing Song, Sep 21 2018

LINKS

Wikipedia, abc conjecture

EXAMPLE

a(2) = 81 because there are exactly 2 abc-hits ((1, 80, 81) and (32, 49, 81)) with third member 81 and count of abc-hits with fixed third member c isn't equal to 2 for every c < 81.

CROSSREFS

KEYWORD

nonn,hard,more

AUTHOR

Vladimir Letsko, Apr 23 2016

STATUS

approved