A115986 Primes p such that the average of p and nextprime(p) is a power of 3.

7, 79, 387420479, 3486784393, 7509466514979724803946715958257527, 147808829414345923316083210206383297581

Offset

1,1

Links

Ray Chandler, Table of n, a(n) for n = 1..13

Example

Nextprime(387420479) = 387420499 and (387420479 + 387420499)/2 = 387420489 = 3^18.

Prog

(PARI) lista(nn) = for(k=1, nn, if(precprime(3^k-1)+nextprime(3^k+1)==2*3^k, print1(precprime(3^k-1), ", "))); \\ Jinyuan Wang, Feb 26 2020

Crossrefs

Cf. A115987, A115988, A115989.

Sequence in context: A052385 A093947 A222137 * A295843 A085606 A365817

Adjacent sequences: A115983 A115984 A115985 * A115987 A115988 A115989

Keyword

nonn

Author

Giovanni Resta, Feb 10 2006

Status

approved