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A081617 Smallest k such that (product of first n primes)*k+1 is divisible by the (n+1)-th prime. Also (A075306(n)-1)/A002110(n). 1

%I

%S 1,4,3,10,10,2,1,3,17,13,10,34,38,4,51,55,51,29,68,13,59,30,27,45,18,

%T 92,77,82,64,14,68,58,114,68,8,77,42,114,31,98,129,110,43,61,159,35,

%U 109,60,91,149,193,2,38,120,259,147,135,22,140,10,263,285,286,134,308

%N Smallest k such that (product of first n primes)*k+1 is divisible by the (n+1)-th prime. Also (A075306(n)-1)/A002110(n).

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

%o (PARI) for(n=1, 100, p=1; forprime(k=2, prime(n), p=p*k); pn=prime(n+1); s=0; while((s+1)%pn>0, s=s+p); print1(s/p", "))

%Y Cf. A081618 (positions of unity).

%K nonn

%O 1,2

%A _Ralf Stephan_, Mar 24 2003

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Last modified October 4 06:54 EDT 2022. Contains 357237 sequences. (Running on oeis4.)