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 A081618 Numbers n such that (product of first n primes)+1 is divisible by the (n+1)-th prime. Also n such that A075306(n)-1 is equal to A002110(n). Positions of 1 in A081617. 1

%I

%S 1,7,232,430

%N Numbers n such that (product of first n primes)+1 is divisible by the (n+1)-th prime. Also n such that A075306(n)-1 is equal to A002110(n). Positions of 1 in A081617.

%C a(5) is greater than 10^5.

%e The 8th prime, 19, divides 2*3*5*7*11*13*17+1=510511, thus 7 is a member.

%o (PARI) p=1:for(n=1,10^5,p=p*prime(n): if((p+1)%prime(n+1)==0,print1(n",")))

%K nonn,hard,more

%O 1,2

%A _Ralf Stephan_, Mar 24 2003

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