A185313 Start of a sequence of n consecutive primes such that the sum of any three consecutive members is also prime.

2, 2, 5, 5, 5, 17, 17, 53507, 364187, 155650237, 15644021363, 604394270371, 767783880089

Offset

1,1

Comments

a(14) > 1.8*10^14. - Giovanni Resta, Jun 07 2017

Links

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

Example

Vacuously, the sum of every three consecutive members of {2, 3} is prime, so a(2) = 2.  a(4) = 5 because 5 + 7 + 11 and 7 + 11 + 13 are prime.

Prog

(PARI) a(n)=if(n<3, return(2), n-=2); my(len=0, p=2, q=3); forprime(r=5, default(primelimit), if(isprime(p+q+r), if(len++==n, my(t=p); for(i=2, n, t=precprime(t-1)); return(t)), len=0); p=q; q=r) \\ Charles R Greathouse IV, Feb 08 2012

Crossrefs

Cf. A072225.

Sequence in context: A356387 A172417 A158106 * A208301 A069896 A053246

Adjacent sequences: A185310 A185311 A185312 * A185314 A185315 A185316

Keyword

nonn,more

Author

Charles R Greathouse IV, Feb 08 2012

Extensions

a(11) from Charles R Greathouse IV, Feb 10 2012

a(12) from Charles R Greathouse IV, Feb 12 2012

a(13) from Zak Seidov, Jun 03 2017

Status

approved