login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A151900 Singular indices in A139206. 2
19, 24, 53, 59, 67, 68, 73 (list; graph; refs; listen; history; text; internal format)
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 A134255

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 14 16:48 EDT 2021. Contains 343898 sequences. (Running on oeis4.)