OFFSET
1,1
COMMENTS
A squarefree subsequence of triangular numbers (T(n) = n*(n+1)/2).
EXAMPLE
3570 = 2*3*5*7*17 = 84*85/2.
21945 = 3*5*7*11*19 = 209*210/2.
121278 = 2*3*17*29*41 = 492*493/2.
154290 = 2*3*5*37*139 = 555*556/2.
MAPLE
q:= n-> map(i-> i[2], ifactors(n)[2])=[1$5]:
select(q, [seq(n*(n+1)/2, n=0..1000)])[]; # Alois P. Heinz, Oct 05 2022
MATHEMATICA
Select[Accumulate @ Range[600], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1, 1} &] (* Amiram Eldar, Oct 05 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Massimo Kofler, Oct 05 2022
STATUS
approved