OFFSET
0,3
LINKS
Paolo P. Lava, Table of n, a(n) for n = 0..1000
EXAMPLE
3 is in the sequence since 3'=1 and 1 is a triangular number.
4 is not in the sequence since 4'=4 and 4 is not a triangular number.
MAPLE
with(numtheory); P:= proc(q) local a, p, n;
for n from 0 to q do a:=n*add(op(2, p)/op(1, p), p=ifactors(n)[2]);
if type((-1+sqrt(1+8*a))/2, integer) then print(n); fi; od; end: P(10^6); # Paolo P. Lava, Sep 25 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Luca Brigada Villa, Sep 25 2013
STATUS
approved