

A102811


Least k such that, for j from 1 to n, 2*P(k+nj) + 3 are consecutive primes with P(i)= ith prime.


1




OFFSET

1,2


LINKS

Table of n, a(n) for n=1..5.


EXAMPLE

For n = 1, 2*P(1) + 3 = 2*2 + 3 = 7 is prime, so a(1)=1 as P(1)=2.
For n = 2, 2*P(3) + 3 = 2*5 + 3 = 13 is prime, 2*P(4) + 3 = 2*7 + 3 = 17 is a prime consecutive to 13, so a(2)=3 as P(3)=5.


PROG

(PARI) a(n) = {my(m=1, p=vector(n, i, prime(i)), q); while(ispseudoprime(q=(2*p[1]+3)) + sum(k=2, n, (q=nextprime(q+1))==2*p[k]+3) < n, m++; p=concat(p[2..n], nextprime(p[n]+1))); m; } \\ Jinyuan Wang, Mar 20 2020


CROSSREFS

Cf. A089009.
Sequence in context: A337249 A259785 A193623 * A307007 A142600 A212999
Adjacent sequences: A102808 A102809 A102810 * A102812 A102813 A102814


KEYWORD

nonn,hard,more


AUTHOR

Pierre CAMI, Feb 26 2005


STATUS

approved



