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 A090468 Class 13+ primes. 7
 545587687, 852480757, 1048438561, 1150849009, 1323457987, 1745980517, 1756123441, 1785398401, 1798736161, 1892507347, 1937020021, 2002155601, 2136716521, 2150905573, 2229004913, 2548101601, 2671514917, 2838761021 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES R. K. Guy, Unsolved Problems in Number Theory, A18. LINKS M. F. Hasler, Table of n, a(n) for n=1..850 MAPLE For Maple program see Mathar link. MATHEMATICA 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[195000000], ClassPlusNbr[ Prime[ # ]] == 13 &]] CROSSREFS Cf. A005113, A005105, A005106, A005107, A005108, A081633, A081634, A081635, A081636, A081637, A081638, A081639, A084071. Sequence in context: A122970 A204779 A172619 * A214480 A071135 A186961 Adjacent sequences:  A090465 A090466 A090467 * A090469 A090470 A090471 KEYWORD nonn AUTHOR Robert G. Wilson v, Nov 26 2003 STATUS approved

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