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A086507 If n is even, a(n) = smallest prime == 1 (mod n), If n is odd, a(n) = smallest prime == -1 (mod n).

%I A086507 #9 Dec 09 2020 19:59:28
%S A086507 2,3,2,5,19,7,13,17,17,11,43,13,103,29,29,17,67,19,37,41,41,23,137,73,
%T A086507 149,53,53,29,173,31,61,97,131,103,139,37,73,191,233,41,163,43,257,89,
%U A086507 89,47,281,97,97,101,101,53,211,109,109,113,113,59,353,61,487,311,251
%N A086507 If n is even, a(n) = smallest prime == 1 (mod n), If n is odd, a(n) = smallest prime == -1 (mod n).
%H A086507 Robert Israel, <a href="/A086507/b086507.txt">Table of n, a(n) for n = 1..10000</a>
%p A086507 f:= proc(n) local x;
%p A086507 if n::even then x:= 1 else x:= -1; fi;
%p A086507 do
%p A086507   x:= x+n;
%p A086507   if isprime(x) then return x fi
%p A086507 od
%p A086507 end proc:
%p A086507 map(f, [$1..100]); # _Robert Israel_, Dec 09 2020
%Y A086507 Cf. A034694, A038700, A086508.
%K A086507 nonn
%O A086507 1,1
%A A086507 _Amarnath Murthy_, Jul 29 2003
%E A086507 More terms from _David Wasserman_, Mar 09 2005