A135368 a(n) = (nextprime(12*n) - previousprime(12*n))/2.

1, 3, 3, 3, 1, 1, 3, 4, 1, 7, 3, 5, 3, 3, 1, 1, 6, 6, 1, 1, 3, 3, 3, 5, 7, 1, 7, 3, 1, 4, 3, 3, 4, 4, 1, 1, 3, 4, 6, 4, 4, 3, 6, 9, 9, 5, 3, 3, 3, 1, 3, 6, 5, 3, 1, 6, 4, 5, 4, 4, 3, 4, 3, 4, 7, 5, 6, 5, 1, 7, 7, 7, 7, 10, 10, 4, 5, 4, 3, 7, 3, 4, 3, 6, 1, 1, 5, 5, 3, 9, 1, 3, 4, 3, 11, 1, 4, 5, 3, 4, 6, 3, 3, 6

Offset: 1

Author

Zak Seidov, Feb 17 2008

Keywords

• nonn

Comments

a(n)=1 if 12n -/+ 1 are twin primes. Corresponding n's are in A124519: 1,5,6,9,15,16,19,20,26,29,35,36,50,...

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A124519, A135023.

Programs

Mathematica

Table[ ( NextPrime[12*n, 1] - NextPrime[12*n, -1] )/2, {n, 1, 25}] (* G. C. Greubel, Oct 11 2016 *)

PARI

a(n) = (nextprime(12*n) - precprime(12*n))/2; \\ Michel Marcus, Oct 12 2016