A151900 Singular indices in A139206.

19, 24, 53, 59, 67, 68, 73

Offset

1,1

Comments

Definition: Singular indices in A139206 are numbers n for which there exists no prime p such that p!/n-1 is prime or, if such a prime p exists, it is very big.

I frown upon this "definition" and the notion of "very big", especially because A139206(24)=3361 seems to be considered to be "very big"(?!)... A more rigorous definition should be given. - M. F. Hasler, Nov 03 2013

Links

Table of n, a(n) for n=1..7.

Example

From M. F. Hasler, Nov 03 2013: (Start)
The first unknown term in A139206 is A139206(19), which is (if it exists) larger than 25000. Therefore a(1)=19.
The term A139206(24)=3361 is "quite large", therefore a(2)=24.
The next unknown term in A139206 is A139206(53), which is also larger than 25000, if it exists. Therefore a(3)=53. (End)

Crossrefs

Cf. A139074, A139206, A151901.

Sequence in context: A297575 A093020 A105504 * A087951 A175356 A363802

Adjacent sequences: A151897 A151898 A151899 * A151901 A151902 A151903

Keyword

hard,more,nonn

Author

Artur Jasinski, Apr 12 2008

Extensions

Edited, corrected and extended by M. F. Hasler, Nov 03 2013

Status

approved