A102811 Least k such that, for j from 1 to n, 2*P(k+n-j) + 3 are consecutive primes with P(i)= i-th prime.

1, 3, 44, 62178, 643266

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: A259785 A369944 A193623 * A307007 A142600 A212999

Adjacent sequences: A102808 A102809 A102810 * A102812 A102813 A102814

Keyword

nonn,hard,more

Author

Pierre CAMI, Feb 26 2005

Status

approved