OFFSET
1,1
COMMENTS
A squarefree subsequence of centered triangular numbers.
EXAMPLE
9010 = 2 * 5 * 17 * 53 = (3 * 78 * (78 - 1) / 2) + 1.
20710 = 2 * 5 * 19 * 109 = (3 * 118 * (118 - 1) / 2) + 1.
39610 = 2 * 5 * 17 * 233 = (3 * 163 * (163 - 1) / 2) + 1.
MATHEMATICA
Select[Table[3*n*(n - 1)/2 + 1, {n, 1, 1000}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* Amiram Eldar, Jan 15 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Massimo Kofler, Jan 15 2023
STATUS
approved