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Search: id:A138965
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| A138965 |
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Least prime factor of concatenation of first n odd numbers. |
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+0
2
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| 13, 3, 23, 37, 3, 11617, 5, 3, 135791113151719, 29, 3, 5, 11, 3, 135791113151719212325272931, 17, 3, 7, 13, 3, 131, 5, 3, 11, 25471443030907588399109, 3, 5, 7, 3, 181, 41, 3
(list; graph; listen)
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OFFSET
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2,1
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LINKS
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F. Smarandache, Sequences of numbers involved in unsolved problems, arXiv:math/0604019
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FORMULA
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A138965(n) = A020639(A019519(n)) (= 3 if n = 0 (mod 3)).
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PROGRAM
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(PARI) t=1; for( n=2, 99, print1( factor( eval( t=Str( t, 2*n-1 )))[1, 1], ", "))
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CROSSREFS
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Cf. A019519, A046036, A048847; A109837, A104644.
Adjacent sequences: A138962 A138963 A138964 this_sequence A138966 A138967 A138968
Sequence in context: A113172 A128154 A107806 this_sequence A005602 A010219 A056139
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KEYWORD
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base,hard,more,nonn
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AUTHOR
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M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Apr 14 2008
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