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

Author

Charles R Greathouse IV, Feb 08 2012

Keywords

• nonn
• more

Comments

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

Examples

			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.
		

Crossrefs

Cf. A072225.

Programs

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

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