A295124 a(n) = smallest number k with n prime factors such that 2d + k/d is prime for every d | k.

1, 3, 15, 105, 93081

Offset

0,2

Comments

Such k must be an odd squarefree number.

a(n) has 2^n divisors and each gives another prime.

Conjecture: the sequence is infinite. It is hard to believe!

a(n) is the smallest k such that A088627(k) = A000005(k) = 2^n.

Links

Table of n, a(n) for n=0..4.

Formula

a(n) = A293756(n+1)/2.

Crossrefs

Cf. A088627, A293756.

Subsequence of A244520 (2d + k/d is prime for every d|k).

Sequence in context: A231634 A353587 A128276 * A107878 A218688 A120016

Adjacent sequences: A295121 A295122 A295123 * A295125 A295126 A295127

Keyword

nonn,more

Author

Thomas Ordowski, Nov 15 2017

Extensions

a(4) from Michel Marcus, Nov 15 2017

Status

approved