OFFSET
1,1
COMMENTS
From Jianing Song, Aug 01 2018: (Start)
k^3 - 1 is a term iff k - 1 and k^2 + k + 1 are both prime.
Is this sequence infinite? That is, are there infinitely many primes p such that p^2 + 3*p + 3 is also prime?
(End)
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..2474
FORMULA
a(n) = A096175(n-1)^3 - 1 for n > 1. - Jianing Song, Aug 01 2018
EXAMPLE
a(1) = 26 = 3^3 - 1 = 26 = 2 * 13, is a semiprime.
a(2) = 215 = 6^3 - 1 = 215 = 5 * 43, is a semiprime.
MAPLE
MATHEMATICA
Select[Table[n^3 - 1, {n, 100}], PrimeOmega[#] == 2 &]
Select[Range[700]^3-1, PrimeOmega[#]==2&] (* Harvey P. Dale, Jan 25 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
K. D. Bajpai, May 09 2014
EXTENSIONS
First Mathematica program corrected by Harvey P. Dale, Jan 25 2019
STATUS
approved