A102811 - OEIS

%I #10 Mar 20 2020 10:01:32

%S 1,3,44,62178,643266

%N 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.

%e For n = 1, 2*P(1) + 3 = 2*2 + 3 = 7 is prime, so a(1)=1 as P(1)=2.

%e 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.

%o (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

%Y Cf. A089009.

%K nonn,hard,more

%O 1,2

%A _Pierre CAMI_, Feb 26 2005