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A083239
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First order recursion: a[0]=1; a(n)=phi[n]-a(n-1)=A000010[n]-a(n-1).
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0
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0, 1, 1, 1, 3, -1, 7, -3, 9, -5, 15, -11, 23, -17, 25, -17, 33, -27, 45, -37, 49, -39, 61, -53, 73, -61, 79, -67, 95, -87, 117, -101, 121, -105, 129, -117, 153, -135, 159, -143, 183, -171, 213, -193, 217, -195, 241, -225, 267, -247, 279, -255, 307, -289, 329, -305, 341, -313, 371, -355, 415, -385, 421, -389, 437, -417
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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COMMENTS
| Provide interesting decomposition: phi(n)=u+w, where u and w consecutive terms of this sequence; Depends also on initial value.
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EXAMPLE
| It follows that a(n)+a(n-1)=A000010(n)
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MATHEMATICA
| f[x_] := EulerPhi[x]-f[x-1] f[0]=1; Table[f[w], {w, 1, 100}]
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CROSSREFS
| Cf. A000213, A083236, A083237, A083238, A000010.
Sequence in context: A161942 A053092 A115873 * A189050 A095868 A140962
Adjacent sequences: A083236 A083237 A083238 * A083240 A083241 A083242
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KEYWORD
| sign
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Apr 23 2003
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