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%I #15 May 08 2021 11:51:16
%S 0,1,1,3,1,5,1,3,4,4,3,5,2,6,13,5,6,1,9,28,8,2,10,8,5,8,3,3,31,2,2,9,
%T 6,1,3,6,2,5,4,1,10,3,7,3,6,7,4,4,1,14,1,1,4,4,18,1,8,1,3,10,3,1,6,1,
%U 7,2,26,19,6,2,8,30,23,6,19,5,1,1,12,1,7
%N Smallest k>=0 such that prime(n)*prime(n+k) + 2 is prime.
%C A dual sequence to A243154. The sequence contains a unique zero term. Indeed, every prime p>3 has the form 3*k +/- 1. So, p^2 + 2 == 0 (mod 3).
%t skp[n_]:=Module[{c=Prime[n],k=0},While[!PrimeQ[c*Prime[n+k]+2],k++];k]; Array[ skp,90,2] (* _Harvey P. Dale_, May 08 2021 *)
%o (PARI) vector(200, n, k=0; while(!isprime(prime(n+1)*prime(n+1+k)+2), k++); k) \\ _Colin Barker_, May 31 2014
%Y Cf. A243154.
%K nonn
%O 2,4
%A _Vladimir Shevelev_, May 31 2014
%E More terms from _Colin Barker_, May 31 2014
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