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Search: id:A072164
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| A072164 |
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Numbers n (>= 1) such that f(n) = n^n - (n-1)^(n-1) is prime. |
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+0
6
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OFFSET
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1,1
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COMMENT
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Enoch Haga proposed studying the primality of f(n) and he already knew the first 4 solutions. C. Rivera found the next four solutions using Ubasic and the last one using PRIMEFORM. Currently f(1907) is only a probable prime number, according to PRIMEFORM.
No other n<25000. - T. D. Noe (noe(AT)sspectra.com), Jun 12 2008
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LINKS
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C. Rivera, Puzzle 185
Eric Weisstein's World of Mathematics, Power Difference Prime
Eric Weisstein's World of Mathematics, Integer Sequence Primes
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EXAMPLE
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2^2 - 1^1 = 3 = prime
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MATHEMATICA
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Select[Range[2, 200], PrimeQ[ #^#-(#-1)^(#-1)]&] (T. D. Noe)
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CROSSREFS
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Cf. A007781 (n^n-(n-1)^(n-1)). Equals A140669 + 1.
Sequence in context: A165407 A039897 A050193 this_sequence A060987 A006259 A119015
Adjacent sequences: A072161 A072162 A072163 this_sequence A072165 A072166 A072167
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KEYWORD
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hard,nonn
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AUTHOR
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Carlos B. Rivera F. (crivera(AT)primepuzzles.net), Jun 28 2002
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EXTENSIONS
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7918 found by Henri Lifchitz in 2001, contributed by Eric Weisstein (eric(AT)weisstein.com), Nov 29, 2005
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