OFFSET
1,1
COMMENTS
A squarefree subsequence of tetrahedral numbers.
EXAMPLE
7770 = 35*36*37/6 = 2*3*5*7*37
14190 = 43*44*45/6 = 2*3*5*11*43
98770 = 83*84*85/6 = 2*5*7*17*83
121485 = 89*90*91/6 = 3*5*7*13*89
MAPLE
q:= n-> is(map(x-> x[2], ifactors(n)[2])=[1$5]):
select(q, [n*(n+1)*(n+2)/6$n=1..500])[]; # Alois P. Heinz, Jun 15 2022
MATHEMATICA
Select[Table[n*(n+1)*(n+2)/6, {n, 1, 400}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1, 1} &] (* Amiram Eldar, Jun 15 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Massimo Kofler, Jun 15 2022
STATUS
approved