1,1

All terms are primes. Note that first 3 terms (3, 7, 127} are primes of the form 2^q - 1, where q = {2, 3, 7) is prime too. Corresponding primes of the form (2^n + 9^n)/11 are {67, 434827, ...}.

Do[p=Prime[n]; f=(2^p+9^p)/11; If[PrimeQ[f], Print[{p, f}]], {n, 1, 100}]

Cf. A000978 = numbers n such that (2^n + 1)/3 is prime. Cf. A057469 = numbers n such that (2^n + 3^n)/5 is prime. Cf. A082387 = numbers n such that (2^n + 5^n)/7 is prime.

Sequence in context: A066771 A139159 A042329 this_sequence A128071 A079622 A005844

Adjacent sequences: A125953 A125954 A125955 this_sequence A125957 A125958 A125959

hard,more,nonn

Alexander Adamchuk (alex(AT)kolmogorov.com), Feb 06 2007

2 more terms from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Feb 14 2007