A037271 -id:A037271 - cp's OEIS frontend

A046426 Numbers requiring 6 steps to reach a prime under the prime factor concatenation procedure.

45, 64, 153, 156, 169, 186, 190, 195, 258, 304, 325, 381, 396, 464, 493, 561, 575, 602, 646, 652, 662, 713, 725, 825, 843, 879, 880, 899, 944, 948, 951, 957, 988, 989, 1007, 1048, 1106, 1121, 1166, 1239, 1252, 1265, 1267, 1293, 1390, 1422, 1474, 1480, 1486

Offset: 1

Patrick De Geest, Jun 15 1998

Patrick De Geest, Home Primes

Cf. A037271, A046411.

Edited by Charles R Greathouse IV, Apr 28 2010

A046427 Numbers requiring 7 steps to reach a prime under the prime factor concatenation procedure.

Original entry on oeis.org

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

Patrick De Geest, Jun 15 1998

Patrick De Geest, Home Primes

Cf. A037271, A046411.

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 *)

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

cp's OEIS Frontend

A046426 Numbers requiring 6 steps to reach a prime under the prime factor concatenation procedure.

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