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Search: id:A126017
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| A126017 |
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Smallest prime of the form k^n + k^(n-1) - 1. |
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+0
2
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| 2, 5, 11, 23, 47, 971, 191, 383, 22136835839, 1310719, 2259801991, 6143, 353563778431304822783, 91424858111, 5425784582791, 57395627, 21474836479, 1099999999999999999, 786431, 13508517176729920889
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Primes arising in A125973.
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EXAMPLE
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Consider n = 10. k^n + k^(n-1) - 1 evaluates to 1, 1535, 78731, 1310719 for k = 1, ..., 4. Only the last of these numbers, 4^10+4^9-1 = 1310719, is prime, hence a(10) = 1310719.
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PROGRAM
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(PARI) {for(n=1, 20, k=1; while(!isprime(a=k^n+k^(n-1)-1), k++); print1(a, ", "))} - Klaus Brockhaus, Dec 17 2006
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CROSSREFS
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Cf. A000040, A045546, A125881-A125885, A125965-A125973.
Sequence in context: A055011 A007505 A059411 this_sequence A034468 A130668 A083380
Adjacent sequences: A126014 A126015 A126016 this_sequence A126018 A126019 A126020
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Dec 14 2006
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EXTENSIONS
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Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Dec 17 2006
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