A046427 Numbers requiring 7 steps to reach a prime under the prime factor concatenation procedure.
91, 128, 196, 305, 344, 416, 438, 456, 554, 656, 690, 707, 746, 750, 779, 897, 910, 950, 1014, 1060, 1098, 1122, 1199, 1209, 1247, 1380, 1507, 1545, 1606, 1679, 1680, 1700, 1711, 1769, 1833, 1884, 1887, 1888, 1928, 1971, 1984, 2000, 2169, 2176, 2192, 2198
Offset: 1
Links
- Patrick De Geest, Home Primes
Programs
-
Mathematica
numberSteps[x_]:=Module[{n,steps,digits,i},n=x; steps=0; While[ !PrimeQ[n]&&steps<10,factors=FactorInteger[n]; digits={}; For[i=1,i<=Length[factors],i++, digits=Join[digits, Flatten[ Table[IntegerDigits[factors[[i,1]]],{factors[[i,2]]}]]];]; n=FromDigits[digits]; steps++;]; Return[steps]]; For[i=1,i<2000,i++,If[numberSteps[i]==7,Print[i];];]; (* Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 16 2006 *)
Extensions
More terms from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 16 2006
Extended and edited by Charles R Greathouse IV, Apr 28 2010