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A085064 a(n) = smallest k such that nk-1 as well as n+k are primes.

%I A085064 #7 May 14 2018 16:04:38
%S A085064 4,3,2,1,6,1,6,3,2,3,12,1,18,3,2,3,6,1,12,3,2,9,6,7,6,15,2,3,12,1,30,
%T A085064 15,4,3,12,5,24,3,8,21,12,1,18,3,2,57,6,5,12,3,2,9,6,5,12,3,2,3,42,1,
%U A085064 18,9,4,3,6,7,6,15,2,27,18,1,66,15,8,3,6,5,120,3,8,15,18,5,12,3,2,15,18
%N A085064 a(n) = smallest k such that nk-1 as well as n+k are primes.
%C A085064 a(n)=1 if and only if n is in A014574. - _Robert Israel_, May 14 2018
%H A085064 Robert Israel, <a href="/A085064/b085064.txt">Table of n, a(n) for n = 1..10000</a>
%p A085064 f:= proc(n) local k;
%p A085064 for k from 1+(n mod 2) by 2 do
%p A085064   if isprime(n+k) and isprime(n*k-1) then return k fi
%p A085064 od
%p A085064 end proc:
%p A085064 map(f, [$1..100]); # _Robert Israel_, May 14 2018
%Y A085064 Cf. A014574, A085063.
%K A085064 nonn
%O A085064 1,1
%A A085064 _Amarnath Murthy_, Jun 28 2003
%E A085064 More terms from _Robert Israel_, May 14 2018