cp's OEIS Frontend

A124993 Primes of the form 22k+1 generated recursively. Initial prime is 23. General term is a(n) = Min {p is prime; p divides (R^11 - 1)/(R - 1); p == 1 (mod 11)}, where Q is the product of previous terms in the sequence and R = 11*Q.

%I A124993 #24 Feb 11 2024 14:20:12
%S A124993 23,4847239,2971,3936923,9461,1453,331,81373909,89,
%T A124993 920771904664817214817542307,353,401743,17088192002665532981,11617
%N A124993 Primes of the form 22k+1 generated recursively. Initial prime is 23. General term is a(n) = Min {p is prime; p divides (R^11 - 1)/(R - 1); p == 1 (mod 11)}, where Q is the product of previous terms in the sequence and R = 11*Q.
%C A124993 All prime divisors of (R^11 - 1)/(R - 1) different from 11 are congruent to 1 modulo 22.
%D A124993 M. Ram Murty, Problems in Analytic Number Theory, Springer-Verlag, NY, (2001), pp. 208-209.
%e A124993 a(3) = 2971 is the smallest prime divisor congruent to 1 mod 22 of (R^11-1)/(R-1) =
%e A124993 7693953366218628230903493622259922359469805176129784863956847906415055607909988155588181877
%e A124993 = 2971 * 357405886421 * 914268562437006833738317047149 * 7925221522553970071463867283158786415606996703, where Q = 23 * 4847239, and R = 11*Q.
%t A124993 a={23}; q=1;
%t A124993 For[n=2,n<=2,n++,
%t A124993     q=q*Last[a]; r=11*q;
%t A124993     AppendTo[a,Min[Select[FactorInteger[(r^11-1)/(r-1)][[All,1]],Mod[#,11]==1 &]]];
%t A124993     ];
%t A124993 a (* _Robert Price_, Jul 14 2015 *)
%Y A124993 Cf. A000945, A057204-A057208, A051308-A051335, A124984-A124993, A125037-A125045.
%K A124993 more,nonn
%O A124993 1,1
%A A124993 _Nick Hobson_, Nov 18 2006
%E A124993 More terms from _Max Alekseyev_, May 29 2009