# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a280005
Showing 1-1 of 1

%I A280005 #69 Jun 13 2023 15:41:33
%S A280005 2,3,13,43,73,47,457,1697,109,8161,10429,13183,30089,66569,5281
%N A280005 Least prime p such that p^n + 1 is the product of n distinct primes.
%C A280005 Corresponding values of p^n + 1 are 3, 10, 2198, 3418802, 2073071594, 10779215330, 4163067000501310394, ...
%C A280005 a(16) <= 206874667. - _Daniel Suteu_, Dec 09 2022
%e A280005 a(2) = 3; 3^2 + 1 = 2 * 5.
%e A280005 a(3) = 13; 13^3 + 1 = 2 * 7 * 157.
%e A280005 a(4) = 43; 43^4 + 1 = 2 * 17 * 193 * 521.
%o A280005 (PARI) a(n) = my(p=2); while (!issquarefree(p^n+1) || omega(p^n+1) != n, p = nextprime(p+1)); p;
%Y A280005 Cf. A000961, A005117, A362957.
%K A280005 nonn,hard,more
%O A280005 1,1
%A A280005 _Altug Alkan_, Feb 24 2017

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE