%I A127997
%S A127997 2,5,79,101,359,857,4463,9029,27823
%N A127997 Numbers n such that (22^n - 1)/21 is prime.
%C A127997 9029 is a term found by Richard Fischer in 2004. - Alexander Adamchuk 
               (alex(AT)kolmogorov.com), Feb 11 2007
%D A127997 H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.
%H A127997 H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">
               Mersenne and Fermat primes field</a>
%t A127997 Select[Prime[Range[100]],PrimeQ[(22^#-1)/21]&]
%Y A127997 Cf. A028491, A004061, A004062, A004063, A004023, A005808, A004064, A016054, 
               A006032, A006033, A006034, A006035. Cf. A127995, A127996, A127998, 
               A127999, A128000, A098438, A128002, A128003, A128004, A128005.
%Y A127997 Sequence in context: A102983 A038583 A082080 this_sequence A096266 A123978 
               A120798
%Y A127997 Adjacent sequences: A127994 A127995 A127996 this_sequence A127998 A127999 
               A128000
%K A127997 hard,more,nonn
%O A127997 1,1
%A A127997 Alexander Adamchuk (alex(AT)kolmogorov.com), Feb 11 2007
%E A127997 More terms from Ryan Propper (rpropper(AT)stanford.edu), Mar 29 2007
%E A127997 27823 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008