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
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.
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Artur Jasinski, Apr 12 2008
EXTENSIONS
Edited, corrected and extended by M. F. Hasler, Nov 03 2013
STATUS
approved