This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A061285 #17 Jun 24 2022 20:11:26 %S A061285 2,4,8,32,64,256,512,2048,16384,32768,262144,1048576,2097152,8388608, %T A061285 67108864,536870912,1073741824,8589934592,34359738368,68719476736, %U A061285 549755813888,2199023255552,17592186044416,281474976710656,1125899906842624,2251799813685248 %N A061285 a(n) = 2^((prime(n) - 1)/2). %C A061285 Square root of 2^(prime(n) - 1), i.e., the smallest number that has prime(n) divisors. %H A061285 <a href="/index/Di#divseq">Index to divisibility sequences</a> %F A061285 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 A061285 Sum_{n>=1} 1/a(n) = A217054. - _Amiram Eldar_, Dec 23 2020 %t A061285 Table[2^((Prime[n] - 1)/2), {n, 2, 25}] (* _Amiram Eldar_, Dec 23 2020 *) %Y A061285 Cf. A000005, A000010, A005097, A005179, A006005, A006093, A034785, A217054. %K A061285 nonn %O A061285 2,1 %A A061285 _Labos Elemer_, May 22 2001