OFFSET
1,1
COMMENTS
The first term with more than two triples is 38601360, corresponding to (a,b,c) = (1794, 21516, 1656), (3180, 12138, 2520) and (6015, 6417, 3105).
LINKS
Robert Israel, Table of n, a(n) for n = 1..162
EXAMPLE
a(3)=22425 is a member because we can take (a,b,c)=(149,150,75) or (42,533,39):
22425 = (149+150)*75 = 149*150+75 = (42+533)*39 = 42*533+39.
MAPLE
N:= 10^7: # for terms <= N
Res:= NULL:
for a from 3 to N/3 do
for b from 3 to a while a*b < N do
c:= a*b/(a+b-1);
if c::posint and c>1 then
v:= (a+b)*c;
if v<=N then Res:= Res, v fi
fi
od od:
S:= sort([Res]):
J:= select(i -> S[i+1]=S[i], [$1..nops(S)-1]):
sort(convert(convert(S[J], set), list));
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel, Nov 06 2019
STATUS
approved