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 A110849 Consider the sequence b(0)=127 and for n>0, b(n) is the least prime of the form k * b(n-1)^2 - 1 where k is a multiple of 6. This sequence gives the values of k. 0
 30, 42, 30, 84, 516, 768, 804, 4806, 2838, 174, 23418, 22770 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 127, 30*127^2-1, 42*(30*127^2-1)^2-1, 30*(42*(30*127^2-1)^2-1)^2-1, 84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1, 516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1, 768*(516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1)^2-1, 804*(768*(516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1, 4806*(804*(768*(516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1, 2838*(4806*(804*(768*(516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1, 174*(2838*(4806*(804*(768*(516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1, 23418*(174*(2838*(4806*(804*(768*(516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1, and 22770*(23418*(174*(2838*(4806*(804*(768*(516*(84*(30*(42*(30*127^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1)^2-1, are primes. MATHEMATICA lpf[{n_, t_}]:=Module[{a=t^2, k=6}, While[!PrimeQ[k*a-1], k=k+6]; {k, k*a-1}]; Rest[ NestList[lpf, {127, 127}, 12][[All, 1]]] (* Harvey P. Dale, Apr 25 2017 *) CROSSREFS Sequence in context: A039297 A043900 A103098 * A074696 A127663 A008885 Adjacent sequences:  A110846 A110847 A110848 * A110850 A110851 A110852 KEYWORD nonn,more AUTHOR Pierre CAMI, Sep 17 2005 EXTENSIONS Edited by Ray Chandler, Sep 26 2005 Definition amended by Georg Fischer, Jun 18 2021 STATUS approved

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Last modified January 27 10:00 EST 2022. Contains 350607 sequences. (Running on oeis4.)