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Search: id:A061795
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| A061795 |
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Number of distinct sums phi(i) + phi(j) for 1<=i<=j<=n, phi(k) = A000010(k). |
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1
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| 1, 1, 3, 3, 6, 6, 9, 9, 9, 9, 13, 13, 17, 17, 18, 18, 22, 22, 26, 26, 26, 26, 30, 30, 32, 32, 32, 32, 37, 37, 41, 41, 41, 41, 43, 43, 47, 47, 47, 47, 53, 53, 57, 57, 57, 57, 62, 62, 62, 62, 63, 63, 67, 67, 67, 67, 67, 67, 72, 72, 79, 79, 79, 79, 81, 81, 86, 86, 87, 87, 93, 93
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OFFSET
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1,3
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EXAMPLE
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If the {s+t} sums are generated by adding 2 terms of an S set consisting of n different entries, then at least 1, at most n(n+1)/2=A000217(n) distinct values can be obtained. The set of first n Phi-values gives results falling between these two extremes. E.g. n=10, A000010:{1,1,2,2,4,2,6,4,6,4...}. Additions provide {2,3,4,5,6,7,8,10,12}, i.e. 9 different results. Thus a(10)=9.
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MATHEMATICA
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f[x_] := EulerPhi[x] t0=Table[Length[Union[Flatten[Table[f[u]+f[w], {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]
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CROSSREFS
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A000217, A000010.
Adjacent sequences: A061792 A061793 A061794 this_sequence A061796 A061797 A061798
Sequence in context: A070318 A023842 A165885 this_sequence A110261 A049318 A079551
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jun 22 2001
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