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%I #9 Jan 05 2021 10:52:20
%S 3,5,7,13,19,23,47,71,73,97,109,139,173,239,241,271,283,307,353,443,
%T 449,499,547,563,593,647,683,709,739,743,761,809,839,859,877,907,941,
%U 971,991,1009,1021,1049,1103,1217,1237,1291,1297,1319,1499,1559,1619,1663,1747,1777,1811,1997,2053,2161
%N a(n) is the least prime p such that n*p+b is prime, where b=1 if n is even or 2 if n is odd, and p > a(n-1) if n >= 2.
%H Robert Israel, <a href="/A340339/b340339.txt">Table of n, a(n) for n = 1..10000</a>
%F A340340(n) = n*a(n)+A000034(n).
%e a(4) = 13 because 13 is the least prime p > 7 such that 4*p+1 is prime.
%p f:= proc(n, p0)
%p local p, a, v;
%p if n::odd then a:= 2 else a:= 1 fi;
%p p:= p0;
%p do p:= nextprime(p)
%p until isprime(n*p+a);
%p return p
%p end proc:
%p p:= 2: R:= NULL:
%p for n from 1 to 100 do
%p p:= f(n,p);
%p R:= R, p;
%p od:
%p R;
%Y Cf. A000034, A340340.
%K nonn
%O 1,1
%A _J. M. Bergot_ and _Robert Israel_, Jan 04 2021
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