A091909 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A091909

Numbers n such that (2*n)!/(2*n!)+1 is prime.

%I #6 Jul 15 2019 03:06:59

%S 1,2,3,5,6,11,12,36,95,372,842,2196,4755

%N Numbers n such that (2*n)!/(2*n!)+1 is prime.

%C a(14) > 10000. - _Hugo Pfoertner_, Jul 15 2019

%e a(3)=3 because (2*3)!/(2*3!)+1=720/12+1=61 is prime.

%Y Cf. A091907.

%K nonn,more,hard

%O 1,2

%A _Hugo Pfoertner_, Feb 10 2004

%E a(12) and a(13) from _Hugo Pfoertner_, Jul 15 2019