A067671 The prime factors of n are also prime factors of the decimal encoding (A067599) of the prime factorization of n.

4, 16, 21, 27, 36, 64, 256, 288, 648, 729, 1024, 1444, 1458, 1764, 1936, 2304, 3125, 4096, 4361, 5184, 6272, 7688, 8277, 9408, 11664, 16384, 18432, 19683, 22472, 22987, 26244, 28125, 29403, 31199, 41472, 43264, 59577, 65536, 67712, 73008

Offset: 1

Author

Joseph L. Pe, Feb 04 2002

Keywords

• nonn
• base

Examples

			21 = 3^1 * 7^1 has prime factors 3,7, which are also prime factors of the corresponding decimal encoding 3171 = 3^1 * 7^1 * 151^1.
		

Crossrefs

Cf. A067599.

Programs

Mathematica

(*f gives the decimal encoding of the prime factorization of n*) f[n_] := FromDigits[Flatten[IntegerDigits[FactorInteger[n]]]]; (*g gives the list of prime factors of n*) g[n_] := Module[{a, l, t}, a = FactorInteger[n]; l = Length[a]; Table[a[[i]][[1]], {i, 1, l}]];
(*main routine*) j[n] := Module[{l1 = g[n], l2 = g[f[n]]}, (Intersection[l1, l2] == l1)]; Select[Range[2, 10^5], j[ # ] &]