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 A061285 a(n) = 2^((prime(n) - 1)/2). 3
 2, 4, 8, 32, 64, 256, 512, 2048, 16384, 32768, 262144, 1048576, 2097152, 8388608, 67108864, 536870912, 1073741824, 8589934592, 34359738368, 68719476736, 549755813888, 2199023255552, 17592186044416, 281474976710656, 1125899906842624, 2251799813685248 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS Square root of 2^(prime(n) - 1), i.e., the smallest number that has prime(n) divisors. LINKS Table of n, a(n) for n=2..27. Index to divisibility sequences FORMULA 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 MATHEMATICA Table[2^((Prime[n] - 1)/2), {n, 2, 25}] (* Amiram Eldar, Dec 23 2020 *) CROSSREFS 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 KEYWORD nonn AUTHOR Labos Elemer, May 22 2001 STATUS approved

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Last modified June 15 02:53 EDT 2024. Contains 373402 sequences. (Running on oeis4.)