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a(n) = smallest number m>0 such that prime(n)*prime(n+1)-m is a prime.
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%I #5 Apr 19 2013 06:54:09

%S 1,2,4,4,4,10,6,4,6,12,18,6,4,4,14,6,6,8,6,4,18,4,18,4,6,4,18,6,16,4,

%T 4,8,6,4,16,18,2,10,12,18,18,22,6,10,4,6,2,22,6,4,6,6,34,8,2,18,6,26,

%U 24,30,6,12,6,16,30,10,8,6,22,6,8,4,2,8,18,26,10,4,12,30,10,12,4,24,6,6,6

%N a(n) = smallest number m>0 such that prime(n)*prime(n+1)-m is a prime.

%o (PARI) a(n) = { my(m=0, v = prime(n)*prime(n+1)); while (! isprime(v-m), m++;); return (m);} \\ _Michel Marcus_, Apr 19 2013

%Y Cf. A107059: records in A107058; A106172: positions of records in A107058. Cf. A074928: a(n)>0 such that p(n)*p(n+1)+a(n) is a smallest prime.

%Y Cf. A074928, A107019, A107057, A107059, A106172.

%K nonn

%O 1,2

%A _Zak Seidov_, May 10 2005