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A084317
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Prime-factor set of n is concatenated as follows: 1# factorize n; 2# order prime factors without exponents in order of magnitude; 3# concatenate digits to get a(n) as a decimal number.
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12
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0, 2, 3, 2, 5, 23, 7, 2, 3, 25, 11, 23, 13, 27, 35, 2, 17, 23, 19, 25, 37, 211, 23, 23, 5, 213, 3, 27, 29, 235, 31, 2, 311, 217, 57, 23, 37, 219, 313, 25, 41, 237, 43, 211, 35, 223, 47, 23, 7, 25, 317, 213, 53, 23, 511, 27, 319, 229, 59, 235, 61, 231, 37, 2, 513, 2311, 67
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| a(0)=0 since no prime factors to concatenate;
n=2520=2.2.2.3.3.5.7; factor-set={2,3,5,7}, so
a(2520)=2357;
a(n)=a[squarefree kernel of n].
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MATHEMATICA
| ffi[x_] := Flatten[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] lf[x_] := Length[FactorInteger[x]] nd[x_, y_] := 10*x+y tn[x_] := Fold[nd, 0, x] conc[x_] := Fold[nd, 0, Flatten[IntegerDigits[ba[x]], 1]] Table[conc[w], {w, 1, 128}]
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CROSSREFS
| Cf. A084318, A084319.
Sequence in context: A133568 A120716 A084318 * A037279 A163591 A085307
Adjacent sequences: A084314 A084315 A084316 * A084318 A084319 A084320
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KEYWORD
| base,nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Jun 16 2003
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