OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Semiprime.
Wikipedia, Semiprime.
FORMULA
a(n) = (2*A237038(n))^3 + 1.
EXAMPLE
(2*2)^3 + 1 = 65 = 5*13 is a semiprime, so a(1) = 2.
MATHEMATICA
L = Select[Range[5000], PrimeQ[#] && PrimeQ[(2 #)^2 - 2 # + 1] && PrimeQ[2 # + 1] &]; (2 L)^3 + 1
Select[Table[(2p)^3+1, {p, Prime[Range[1000]]}], PrimeOmega[#]==2&] (* Harvey P. Dale, Jul 21 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Sondow, Feb 02 2014
STATUS
approved