OFFSET
1,1
COMMENTS
A squarefree subsequence of heptagonal numbers.
EXAMPLE
3010 = 2*5*7*43 = 35(5*35-3)/2.
4774 = 2*7*11*31 = 44(5*44-3)/2.
10465 = 5*7*13*23 = 65(5*65-3)/2.
14326 = 2*13*19*29 = 76(5*76-3)/2.
PROG
(Python)
from itertools import count, islice
from sympy import factorint
def A351867_gen(): return filter(lambda k:sum((f := factorint(k)).values()) == 4 == len(f), (n*(5*n-3)//2 for n in count(1)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Massimo Kofler, Apr 12 2022
STATUS
approved