OFFSET
1,2
COMMENTS
Terms that are triangular: 1, 3, 6, 210, 630, 2162160, ...
The number of triangular divisors of a(n) is A007862(a(n)): 1, 2, 3, 5, 6, 7, 8, 9, 10, 12, ...
EXAMPLE
1260 has 36 divisors of which 12 are triangular numbers {1, 3, 6, 10, 15, 21, 28, 36, 45, 105, 210, 630}. No positive integer smaller than 1260 has as many as twelve triangular divisors; hence 1260 is a term.
MATHEMATICA
max=0; Do[If[(d=Length@Select[Divisors@k, IntegerQ[(Sqrt[8#+1]-1)/2]&])>max, Print@k; max=d], {k, 10^10}] (* Giorgos Kalogeropoulos, Jan 13 2022 *)
PROG
(PARI) lista(nn) = my(r=0); for (n=1, nn, my(m = sumdiv(n, d, ispolygonal(d, 3))); if (m>r, r=m; print1(n, ", ")); ); } \\ Michel Marcus, Jan 14 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Bernard Schott, Jan 13 2022
STATUS
approved