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Search: id:A038395
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| A038395 |
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Concatenate the first n odd numbers in reverse order. |
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+0
2
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| 1, 31, 531, 7531, 97531, 1197531, 131197531, 15131197531, 1715131197531, 191715131197531, 21191715131197531, 2321191715131197531, 252321191715131197531, 27252321191715131197531
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n) starts with the digits of 2n-1. Indices of prime or probable prime terms are 1,2,37,62,409,...: see also A089922. - M. F. Hasler, Apr 13 2008
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REFERENCES
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M. Bencze and L.Tutescu, Some Notions and Questions in Number Theory, Sequence 3.
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LINKS
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M. L. Perez et al., eds., Smarandache Notions Journal
Florentin Smarandache, Sequences of Numbers Involved in Unsolved Problems, arXiv:math/0604019.
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FORMULA
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a(n)=(2*n-1)*10^floor{1+log10[a(n-1)]}+a(n-1), with a(1)=1 - Paolo P. Lava (ppl(AT)spl.at), Jun 19 2008
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MAPLE
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P:=proc(i) local a, n; a:=1; print(a); for n from 2 by 1 to i do a:=(2*n-1)*10^floor(evalf(1+log10(a), 100))+a ; print(a); od; end: P(100); - Paolo P. Lava (ppl(AT)spl.at), Jun 19 2008
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PROGRAM
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(PARI) t=""; for( n=1, 10^3, /*ispseudoprime*/( t=eval( Str( 2*n-1, t))) & print(n" "t)) \- M. F. Hasler, Apr 13 2008
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CROSSREFS
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Cf. A089922, A109837, A038394-A038399, A019518-A019519.
Sequence in context: A022595 A125488 A022659 this_sequence A022755 A003533 A005462
Adjacent sequences: A038392 A038393 A038394 this_sequence A038396 A038397 A038398
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KEYWORD
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nonn,base,new
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AUTHOR
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M. I. Petrescu (mipetrescu(AT)yahoo.com)
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EXTENSIONS
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Edited and extended by M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Apr 13 2008
Edited by T. D. Noe (noe(AT)sspectra.com), Oct 30 2008
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