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Search: id:A038194
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| A038194 |
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Iterated sum-of-digits of n-th prime; or digital root of n-th prime; or n-th prime modulo 9. |
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+0
20
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| 2, 3, 5, 7, 2, 4, 8, 1, 5, 2, 4, 1, 5, 7, 2, 8, 5, 7, 4, 8, 1, 7, 2, 8, 7, 2, 4, 8, 1, 5, 1, 5, 2, 4, 5, 7, 4, 1, 5, 2, 8, 1, 2, 4, 8, 1, 4, 7, 2, 4, 8, 5, 7, 8, 5, 2, 8, 1, 7, 2, 4, 5, 1, 5, 7, 2, 7, 4, 5, 7, 2, 8, 7, 4, 1, 5, 2, 1, 5, 4, 5, 7, 8, 1, 7, 2, 8, 7, 2, 4, 8, 2, 1, 5, 4, 8, 5, 8, 1, 1, 7, 8, 5, 2, 4
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Integers with iterated sum-of-digits 3, 6 or 9 are divisible by 3, so 3 is the only prime with iterated sum-of-digits 3 and there are no primes with iterated sum-of-digits 6 or 9.
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EXAMPLE
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Prime(5) = 11, 1 + 1 = 2 hence a(5) = 2.
a(297)=7 because the 297th prime is 1951 and 1+9+5+1 = 16 -> 1+6 = 7.
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PROGRAM
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(PARI) forprime(p=2, 600, print1(p%9, ", "))
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CROSSREFS
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Cf. A007605, A061237 - A061242.
Cf. A010888, A139413..
Sequence in context: A076779 A074464 A074463 this_sequence A111309 A007605 A077765
Adjacent sequences: A038191 A038192 A038193 this_sequence A038195 A038196 A038197
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KEYWORD
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easy,nonn,base
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AUTHOR
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Den Roussel (DenRoussel(AT)webtv.net) and Clark Kimberling (ck6(AT)evansville.edu)
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EXTENSIONS
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Edited by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Feb 16, 2002
Edited by N. J. A. Sloane (njas(AT)research.att.com), May 14 2008 at the suggestion of R. J. Mathar.
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