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A072917
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a(n) = p(n) - phi(n), where p(n) is the least prime greater than phi(n).
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0
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 1, 1, 1, 3, 1, 1, 1, 3, 3, 1, 1, 1, 1, 3, 1, 1, 3, 1, 5, 1, 1, 1, 5, 1, 1, 1, 1, 3, 5, 1, 1, 1, 1, 3, 5, 5, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 5, 5, 3, 1, 5, 3, 5, 1, 5, 1, 1, 1, 1, 1, 5, 1, 5, 5, 1, 1, 5, 3, 1, 3, 1, 1, 5, 1, 3, 1, 1, 1, 5, 1, 1, 1, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,15
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EXAMPLE
| phi(15) = 8 and the least prime > 8 is 11; hence a(15) = 11 - 8 = 3.
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MATHEMATICA
| a[n_] := Module[{r, p}, p = EulerPhi[n]; r = p + 1; While[ ! PrimeQ[r], r = r + 1]; r - p]; Table[a[i], {i, 1, 100}]
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CROSSREFS
| Sequence in context: A114231 A079075 A086703 * A114266 A135910 A107333
Adjacent sequences: A072914 A072915 A072916 * A072918 A072919 A072920
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KEYWORD
| easy,nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Aug 11 2002
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