OFFSET
1,1
COMMENTS
The least positive k for which 2*k^2 + 29 is neither prime nor semiprime is k = 185, which gives 2*k^2 + 29 = 68479 = 31*47^2.
EXAMPLE
a(5) = 39; 2*39^2 + 29 = 3071 = 37*83 is semiprime.
MATHEMATICA
Select[Range[200], PrimeOmega[2*#^2 + 29] == 2 &] (* Amiram Eldar, Apr 15 2022 *)
PROG
(Python)
from sympy import primeomega
def semiprime(n): return primeomega(n) == 2
print([k for k in range(140) if semiprime(2*k**2+29)]) # Michael S. Branicky, Apr 15 2022
(PARI) isok(k) = bigomega(2*k^2+29) == 2; \\ Michel Marcus, Apr 15 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Rémi Guillaume, Apr 15 2022
STATUS
approved