OFFSET
1,2
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..92
MATHEMATICA
A018804[n_]:=Apply[Times, Apply[((#1-1)#2/#1+1)#1^#2&, FactorInteger[n], {1}]]; (* After Amiram Eldar in A018804 *)
upto=10^5; Reap[Do[If[Divisible[k(k+1)/2, A018804[k]], Sow[k]], {k, upto}]][[-1, -1]] (* Paolo Xausa, Aug 19 2022 *)
PROG
(PARI) isok(k) = !(k*(k+1)/2 % sumdiv(k, d, k*eulerphi(d)/d)); \\ Michel Marcus, Nov 27 2021
(Python)
from itertools import islice, count
from sympy import factorint
from math import prod
def A349724(): # generator of terms
for k in count(1):
if not k*(k+1)//2 % prod(p**(e-1)*((p-1)*e+p) for p, e in factorint(k).items()):
yield k
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, Nov 27 2021
EXTENSIONS
a(12)-a(20) from Paolo Xausa, Nov 27 2021
More terms from Amiram Eldar, Nov 27 2021
STATUS
approved