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A136623
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a(n) = largest prime power that is <=n and is coprime to n.
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0
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1, 1, 2, 3, 4, 5, 5, 7, 8, 9, 9, 11, 11, 13, 13, 13, 16, 17, 17, 19, 19, 19, 19, 23, 23, 25, 25, 27, 27, 29, 29, 31, 32, 31, 32, 31, 32, 37, 37, 37, 37, 41, 41, 43, 43, 43, 43, 47, 47, 49, 49, 49, 49, 53, 53, 53, 53, 53, 53, 59, 59, 61, 61, 61, 64, 61, 64, 67, 67, 67, 67, 71, 71, 73
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| a(n) = A031218(n-1) for all n where 2 <= n <= 33.
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EXAMPLE
| The largest prime power that is <= 34 is 32 = 2^5. But 32 is not coprime to 34. The next smaller prime power is 31 = 31^1. 31 is indeed coprime to 34; so a(34) = 31.
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PROG
| (PARI) a(n) = {x=n; while((matsize(factor(x))[1]>1) | (gcd(x, n)!=1), x--); x} [From Michael Porter (michael_b_porter(AT)yahoo.com), Oct 07 2009]
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CROSSREFS
| Cf. A031218.
Sequence in context: A162683 A073137 A131233 * A031218 A163382 A094017
Adjacent sequences: A136620 A136621 A136622 * A136624 A136625 A136626
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Apr 14 2008
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EXTENSIONS
| More terms from Michael Porter (michael_b_porter(AT)yahoo.com), Oct 07 2009
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