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Search: id:A070746
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| A070746 |
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Numbers n such that n 1's followed by n is a prime. |
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+0
4
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OFFSET
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1,2
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COMMENT
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The number corresponding to a(3) has been certified prime with Primo; those corresponding to a(4), a(5), a(6) are probable primes.
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EXAMPLE
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7 is in the sequence because 11111117 (seven 1's followed by 7) is prime.
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MATHEMATICA
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Do[ If[ PrimeQ[ FromDigits[ Join[ IntegerDigits[(10^n - 1)/9], IntegerDigits[n]]]], Print[n]], {n, 1, 2000, 2}]
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PROGRAM
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(WinPFGW) Primality testing r(5107)*10^len(5107)+5107 [N-1/N+1, Brillhart-Lehmer-Selfridge] r(5107)*10^len(5107)+5107 is Fermat and Lucas PRP! (79 seconds). [from Jason Earls]
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CROSSREFS
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Cf. A068817, A084428.
Sequence in context: A163016 A129291 A159815 this_sequence A068004 A098110 A062334
Adjacent sequences: A070743 A070744 A070745 this_sequence A070747 A070748 A070749
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KEYWORD
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base,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), May 03 2002
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EXTENSIONS
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2203 from Jason Earls (zevi_35711(AT)yahoo.com), May 06 2002
4841 from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Sep 02 2002.
5107 from Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Jun 29 2003
11489 from Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Jul 04 2003
Edited by T. D. Noe (noe(AT)sspectra.com), Oct 30 2008
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