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Search: id:A067671
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| A067671 |
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The prime factors of n are also prime factors of the decimal encoding (A067599) of the prime factorization of n. |
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+0
1
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| 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
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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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.
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MATHEMATICA
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(*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[ # ] &]
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CROSSREFS
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Cf. A067599.
Sequence in context: A032827 A071966 A039943 this_sequence A075331 A065661 A100275
Adjacent sequences: A067668 A067669 A067670 this_sequence A067672 A067673 A067674
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Feb 04 2002
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