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A061285
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a(n) = 2^((prime(n) - 1)/2).
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2
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2, 4, 8, 32, 64, 256, 512, 2048, 16384, 32768, 262144, 1048576, 2097152, 8388608, 67108864, 536870912, 1073741824, 8589934592, 34359738368, 68719476736, 549755813888, 2199023255552, 17592186044416, 281474976710656
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OFFSET
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2,1
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COMMENTS
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Square root of 2^(prime(n) - 1), i.e., the smallest number that has prime(n) divisors.
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LINKS
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Table of n, a(n) for n=2..25.
Index to divisibility sequences
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FORMULA
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a(n) = sqrt(min(x; A000005(x) = prime(n))) = sqrt(A034785(n)/2) = sqrt(2^(prime(n) - 1)) = sqrt(2^A006093(n)) = sqrt(2^phi(prime(n))) = sqrt(2^A000010(A000040(n))).
Sum_{n>=1} 1/a(n) = A217054. - Amiram Eldar, Dec 23 2020
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MATHEMATICA
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Table[2^((Prime[n] - 1)/2), {n, 2, 25}] (* Amiram Eldar, Dec 23 2020 *)
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CROSSREFS
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Cf. A000005, A000010, A005097, A005179, A006005, A006093, A034785, A217054.
Sequence in context: A307611 A053147 A128055 * A194810 A271216 A102000
Adjacent sequences: A061282 A061283 A061284 * A061286 A061287 A061288
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KEYWORD
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nonn
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AUTHOR
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Labos Elemer, May 22 2001
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STATUS
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approved
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