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A068346
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a(n) = n'' = second arithmetic derivative of n.
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8
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0, 0, 0, 4, 0, 1, 0, 16, 5, 1, 0, 32, 0, 6, 12, 80, 0, 10, 0, 44, 7, 1, 0, 48, 7, 8, 27, 80, 0, 1, 0, 176, 9, 1, 16, 92, 0, 10, 32, 72, 0, 1, 0, 112, 16, 10, 0, 240, 9, 39, 24, 92, 0, 108, 32, 96, 13, 1, 0, 96, 0, 14, 20, 640, 21, 1, 0, 156, 15, 1, 0, 220, 0, 16, 16, 176, 21, 1, 0, 368, 216
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| a(A000040(n)) = 0; a(A157037(n)) = 1. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 22 2009]
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..2000
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FORMULA
| a(n) = A003415(A003415(n)).
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MATHEMATICA
| dn[0]=0; dn[1]=0; dn[n_]:=Module[{f=Transpose[FactorInteger[n]]}, If[PrimeQ[n], 1, Plus@@(n*f[[2]]/f[[1]])]]; Table[dn[dn[n]], {n, 100}] (T. D. Noe)
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CROSSREFS
| Cf. A003415 (arithmetic derivative of n), A099306 (third arithmetic derivative of n).
Sequence in context: A117436 A166318 A166317 * A006838 A061309 A059064
Adjacent sequences: A068343 A068344 A068345 * A068347 A068348 A068349
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 28 2002
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EXTENSIONS
| More terms from T. D. Noe (noe(AT)sspectra.com), Oct 12 2004
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