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A060845
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Largest prime < a nontrivial power of a prime.
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2
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3, 7, 7, 13, 23, 23, 31, 47, 61, 79, 113, 113, 127, 167, 241, 251, 283, 337, 359, 509, 523, 619, 727, 839, 953, 1021, 1327, 1367, 1669, 1847, 2039, 2179, 2179, 2207, 2399, 2803, 3121, 3469, 3719, 4093, 4483, 4909, 5039, 5323, 6229, 6553, 6857, 6883, 7919
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listen;
history;
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internal format)
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OFFSET
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1,1
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LINKS
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Harry J. Smith, Table of n, a(n) for n = 1..1000
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FORMULA
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a(n) = prevprime[A025475(n)] = A007917[A025475(n)] = Max{p| p < A025475(n)}
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EXAMPLE
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78125=5^7 follows 78121
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MATHEMATICA
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Take[NextPrime[#, -1]&/@Union[Flatten[Table[Prime[p]^n, {n, 2, 20}, {p, 25}]]], 50] (* From Harvey P. Dale, Mar 26 2012 *)
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PROG
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(PARI) { m=1; for (n=1, 1000, m++; while(sigma(m)*eulerphi(m)*(1 - isprime(m)) <= (m - 1)^2, m++); write("b060845.txt", n, " ", precprime(m - 1)); ) } [From Harry J. Smith, Jul 19 2009]
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CROSSREFS
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Cf. A025475, A000961, A001597, A001694, A007917, A007918, A013632, A013633, A049711, A060846.
Sequence in context: A137315 A139795 A118259 * A060215 A059478 A175329
Adjacent sequences: A060842 A060843 A060844 * A060846 A060847 A060848
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), May 03 2001
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STATUS
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approved
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