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%I #17 Jun 24 2022 20:11:26
%S 2,4,8,32,64,256,512,2048,16384,32768,262144,1048576,2097152,8388608,
%T 67108864,536870912,1073741824,8589934592,34359738368,68719476736,
%U 549755813888,2199023255552,17592186044416,281474976710656,1125899906842624,2251799813685248
%N a(n) = 2^((prime(n) - 1)/2).
%C Square root of 2^(prime(n) - 1), i.e., the smallest number that has prime(n) divisors.
%H <a href="/index/Di#divseq">Index to divisibility sequences</a>
%F 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))).
%F Sum_{n>=1} 1/a(n) = A217054. - _Amiram Eldar_, Dec 23 2020
%t Table[2^((Prime[n] - 1)/2), {n, 2, 25}] (* _Amiram Eldar_, Dec 23 2020 *)
%Y Cf. A000005, A000010, A005097, A005179, A006005, A006093, A034785, A217054.
%K nonn
%O 2,1
%A _Labos Elemer_, May 22 2001
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