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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
 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, 92, 77, 82, 64, 14, 68, 58, 114, 68, 8, 77, 42, 114, 31, 98, 129, 110, 43, 61, 159, 35, 109, 60, 91, 149, 193, 2, 38, 120, 259, 147, 135, 22, 140, 10, 263, 285, 286, 134, 308 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE The 8th prime, 19, divides 2*3*5*7*11*13*17+1=510511, thus a(7)=1. PROG (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", ")) CROSSREFS Cf. A081618 (positions of unity). Sequence in context: A075563 A299325 A316196 * A103252 A065763 A185730 Adjacent sequences:  A081614 A081615 A081616 * A081618 A081619 A081620 KEYWORD nonn AUTHOR Ralf Stephan, Mar 24 2003 STATUS approved

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Last modified April 18 10:35 EDT 2019. Contains 322209 sequences. (Running on oeis4.)