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A091310 Primes not of the form p*q + p - q with prime p and q.

%I A091310 #10 Jun 05 2025 15:48:48
%S A091310 2,3,11,23,47,53,59,71,79,83,101,107,131,163,167,173,179,191,223,227,
%T A091310 239,251,263,269,293,311,331,347,359,367,383,419,431,439,443,467,479,
%U A091310 491,503,509,547,563,587,599,607,641,647,653,659,683,691,719,727,733
%N A091310 Primes not of the form p*q + p - q with prime p and q.
%H A091310 Robert Israel, <a href="/A091310/b091310.txt">Table of n, a(n) for n = 1..10000</a>
%p A091310 N:= 1000: # for terms <= N
%p A091310 P:= select(isprime, [2,seq(i,i=3..N,2)]):
%p A091310 nP:= nops(P):
%p A091310 S:= {}:
%p A091310 for i from 1 to nP do
%p A091310   for j from 1 to nP do
%p A091310     x:= P[i]*P[j]+P[i]-P[j];
%p A091310     if x > N then break fi;
%p A091310     if isprime(x) then S:= S union {x} fi
%p A091310 od od:
%p A091310 sort(convert(convert(P,set) minus S, list)); # _Robert Israel_, Jun 05 2025
%t A091310 x = Take[ Select[ Union[ Flatten[ Table[ Prime[p]*Prime[q] + Prime[p] - Prime[q], {p, 116}, {q, 116}]]], PrimeQ[ # ] &], 200]; y = Table[ Prime[i], {i, PrimePi[ p[[ -1]] ]}]; Take[ Complement[y, x], 54] (* _Robert G. Wilson v_ *)
%Y A091310 Primes not in A091301.
%K A091310 nonn
%O A091310 1,1
%A A091310 _Zak Seidov_, Feb 21 2004