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A084071 Class 12+ primes. 9

%I

%S 68198461,115084901,138358573,156811273,213397621,220576331,234432217,

%T 260050573,282261961,290996753,330864497,353653063,371500819,

%U 383616341,406915273,426240379,445800983,446707201,449558323,460339577,472782553

%N Class 12+ primes.

%D R. K. Guy, Unsolved Problems in Number Theory, A18.

%p For Maple program see Mathar link in A005105.

%t PrimeFactors[n_Integer] := Flatten[ Table[ #[[1]], {1}] & /@ FactorInteger[n]]; f[n_Integer] := Block[{m = n}, If[m == 0, m = 1, While[ IntegerQ[m/2], m /= 2]; While[ IntegerQ[m/3], m /= 3]]; Apply[Times, PrimeFactors[m] + 1]]; ClassPlusNbr[n_] := Length[ NestWhileList[f, n, UnsameQ, All]] - 3; Prime[ Select[ Range[25000000], ClassPlusNbr[ Prime[ # ]] == 12 &]]

%Y Cf. A005113, A005105, A005106, A005107, A005108, A081633, A081634, A081635, A081636, A081637, A081638, A081639.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Mar 20 2003

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Last modified May 25 12:30 EDT 2019. Contains 323568 sequences. (Running on oeis4.)