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A165978 Largest prime factor of number formed from a(n-1) with a 1 added at the end, a(1)=2. 1
2, 7, 71, 79, 113, 29, 97, 971, 83, 277, 163, 233, 37, 53, 59, 197, 73, 43, 431, 479, 1597, 15971, 383, 1277, 43, 431, 479, 1597, 15971, 383, 1277, 43, 431, 479, 1597, 15971, 383, 1277, 43, 431, 479, 1597, 15971, 383, 1277, 43, 431, 479, 1597, 15971, 383, 1277 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Conjecture: The same number will never occur twice in this sequence. - Lowell
Disproved - cycle 43,431,479,1597,15971,383,1277 repeats starting at a(18). - Chandler
LINKS
EXAMPLE
Largest prime factor of 21 is 7, so next term after 2 is 7.
MATHEMATICA
NestList[FactorInteger[10#+1][[-1, 1]]&, 2, 60] (* Harvey P. Dale, Nov 10 2020 *)
CROSSREFS
Sequence in context: A319640 A260566 A113866 * A106917 A188665 A198188
KEYWORD
base,nonn
AUTHOR
J. Lowell, Oct 02 2009
EXTENSIONS
Edited and extended by Ray Chandler, Nov 10 2009
STATUS
approved

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Last modified March 28 17:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)