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A303809
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Multiplicative with a(p^k) = 2^a(k).
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3
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1, 2, 2, 4, 2, 4, 2, 4, 4, 4, 2, 8, 2, 4, 4, 16, 2, 8, 2, 8, 4, 4, 2, 8, 4, 4, 4, 8, 2, 8, 2, 4, 4, 4, 4, 16, 2, 4, 4, 8, 2, 8, 2, 8, 8, 4, 2, 32, 4, 8, 4, 8, 2, 8, 4, 8, 4, 4, 2, 16, 2, 4, 8, 16, 4, 8, 2, 8, 4, 8, 2, 16, 2, 4, 8, 8, 4, 8, 2, 32, 16, 4, 2, 16
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OFFSET
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1,2
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COMMENTS
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This sequence contains every power of 2; see A303819 for the corresponding least indices.
For any n > 0, a(n) only depends on the prime signature of n.
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LINKS
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FORMULA
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a(n) <= n with equality iff n = A014221(k) for some k >= 0.
a(A002110(k)) = 2^k for any k >= 0.
a(n) = 2 iff n is prime.
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PROG
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(PARI) a(n) = my (f=factor(n)); prod (i=1, #f~, 2^a(f[i, 2]))
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CROSSREFS
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KEYWORD
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nonn,easy,mult
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AUTHOR
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STATUS
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approved
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