OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
9 = 3 * 3 = 2*(7* 2 - 5)/2.
3961 = 17 * 233 = 34*(7* 34 - 5)/2.
41311 = 109 * 379 = 109*(7*109 - 5)/2.
758881 = 233 * 3257 = 466*(7*466 - 5)/2.
MAPLE
R:= NULL: count:= 0:
for i from 1 while count < 100 do
v:= i*(7*i-5)/2;
if numtheory:-bigomega(v) = 2 then R:= R, v; count:= count+1 fi
od:
R; # Robert Israel, Jan 15 2023
MATHEMATICA
Select[Table[n*(7*n - 5)/2, {n, 1, 600}], PrimeOmega[#] == 2 &] (* Amiram Eldar, Aug 07 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Massimo Kofler, Aug 07 2022
STATUS
approved