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A066820
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Integers of the form phi(n^2+1)/n.
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4
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1, 2, 4, 6, 6, 10, 14, 16, 20, 24, 26, 25, 36, 40, 48, 54, 56, 60, 66, 74, 84, 90, 94, 110, 116, 120, 124, 126, 98, 130, 134, 146, 150, 156, 160, 170, 176, 180, 184, 150, 204, 206, 210, 192, 224, 230, 236, 240, 250, 256, 260, 264, 270, 280, 284, 300, 306, 314, 326
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| If k^2+1 is prime phi(k^2+1)/k=k, hence A005574(n) is included in the sequence.For odd values see A066852.
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
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PROG
| (PARI) { n=0; for (m=1, 10^10, if (eulerphi(m^2 + 1) % m == 0, write("b066820.txt", n++, " ", eulerphi(m^2 + 1) / m); if (n==1000, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Mar 29 2010]
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CROSSREFS
| Cf. A066852.
Sequence in context: A037225 A060685 A073353 * A141677 A087459 A123258
Adjacent sequences: A066817 A066818 A066819 * A066821 A066822 A066823
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Jan 19 2002
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EXTENSIONS
| Term n=51 a=260 added by Harry J. Smith (hjsmithh(AT)sbcglobal.net), Mar 29 2010
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