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A046427
Numbers requiring 7 steps to reach a prime under the prime factor concatenation procedure.
0
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
1,1
LINKS
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 *)
CROSSREFS
Sequence in context: A351336 A328662 A020235 * A179338 A020238 A220171
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Jun 15 1998
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
STATUS
approved