OFFSET
1,1
EXAMPLE
a(1) = 2: 2^2 - 1 = 3 and 2^2 + 1 are both prime,
a(2) = 10: 2^10 - 1 = 1023 = 3 * 11 * 31 and 2^10 + 1 = 1025 = 5^2 * 41 both have 3 prime factors.
MATHEMATICA
Select[Range[200], PrimeOmega[2^# - 1 ] == PrimeOmega[2^# + 1 ] &] (* Amiram Eldar, Aug 24 2019 *)
PROG
(PARI) for(k=1, 209, my(f=bigomega(2^k-1), g=bigomega(2^k+1)); if(f==g, print1(k, ", ")))
(Magma) [m:m in [2..400]| &+[p[2]: p in Factorization(2^m-1)] eq &+[p[2]: p in Factorization(2^m+1)]]; // Marius A. Burtea, Aug 24 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Hugo Pfoertner, Aug 24 2019
EXTENSIONS
More terms from Amiram Eldar, Aug 24 2019
STATUS
approved