OFFSET
1,1
LINKS
Karl-Heinz Hofmann, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1) = 2 * 2 * 2 * 2 = 16
a(2) = 3 * 3 * 2 * 3 = 54
a(3) = 2 * 7 * 3 * 3 = 126
a(4) = 3 * 7 * 2 * 5 = 210.
PROG
(Python)
from sympy import isprime, nextprime, integer_nthroot
c_upto = 100000
A167690, q, lim_q, lim_g = set(), 2, integer_nthroot(c_upto//2, 3)[0], integer_nthroot(c_upto//3, 2)[0]//2
while (g:=q) <= lim_q:
while g <= lim_g:
fac = 2 * q * g
for j in [2 * q - g, 2 * g - q, q * g - 2 ]:
if isprime(j) and (an:= fac * j) < c_upto : A167690.add(an)
g = nextprime(g)
q = nextprime(q)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Nov 09 2009
EXTENSIONS
Corrected (250, 686, 1794 etc inserted, 9486, 15782 removed) by R. J. Mathar, May 30 2010
STATUS
approved
