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

 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 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.

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