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%I #23 Nov 16 2017 02:40:53
%S 1,3,15,105,93081
%N a(n) = smallest number k with n prime factors such that 2d + k/d is prime for every d | k.
%C Such k must be an odd squarefree number.
%C a(n) has 2^n divisors and each gives another prime.
%C Conjecture: the sequence is infinite. It is hard to believe!
%C a(n) is the smallest k such that A088627(k) = A000005(k) = 2^n.
%F a(n) = A293756(n+1)/2.
%Y Cf. A088627, A293756.
%Y Subsequence of A244520 (2d + k/d is prime for every d|k).
%K nonn,more
%O 0,2
%A _Thomas Ordowski_, Nov 15 2017
%E a(4) from _Michel Marcus_, Nov 15 2017