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 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); Mod[p,11]=1}, where Q is the product of previous terms in the sequence and R = 11Q. 18
 23, 4847239, 2971, 3936923, 9461, 1453, 331, 81373909, 89, 920771904664817214817542307, 353, 401743, 17088192002665532981, 11617 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All prime divisors of (R^11 - 1)/(R - 1) different from 11 are congruent to 1 modulo 22. REFERENCES M. Ram Murty, Problems in Analytic Number Theory, Springer-Verlag, NY, (2001), pp. 208-209. LINKS N. Hobson, Home page (listed in lieu of email address) EXAMPLE a(3) = 2971 is the smallest prime divisor congruent to 1 mod 22 of (R^11-1)/(R-1) = 7693953366218628230903493622259922359469805176129784863956847906415055607909988155588181877 = 2971 * 357405886421 * 914268562437006833738317047149 * 7925221522553970071463867283158786415606996703, where Q = 23 * 4847239, and R = 11Q. MATHEMATICA a={23}; q=1; For[n=2, n<=2, n++,     q=q*Last[a]; r=11*q;     AppendTo[a, Min[Select[FactorInteger[(r^11-1)/(r-1)][[All, 1]], Mod[#, 11]==1 &]]];     ]; a (* Robert Price, Jul 14 2015 *) CROSSREFS Cf. A000945, A057204-A057208, A051308-A051335, A124984-A124993, A125037-A125045. Sequence in context: A320442 A034247 A050234 * A013818 A290118 A087527 Adjacent sequences:  A124990 A124991 A124992 * A124994 A124995 A124996 KEYWORD more,nonn AUTHOR Nick Hobson, Nov 18 2006 EXTENSIONS More terms from Max Alekseyev, May 29 2009 STATUS approved

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Last modified April 1 02:10 EDT 2020. Contains 333153 sequences. (Running on oeis4.)