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 A289275 #17 Jul 27 2017 02:39:25 %S A289275 1,2,4,8,16,32,46,64,128,256,284,512,1024,1633,2048,4096,8192,16384, %T A289275 32768,65536,131072,149728,242656,260495,262144,298057,524288,1048576, %U A289275 1056752,2097152,4194304,8388608,9587584,16777216,17706256,33554432,67108864,134217728 %N A289275 Numbers k such that the deficiency of k^2 is itself a square. %C A289275 The sequence of square roots of the deficiencies of this sequence is A288145. %C A289275 The current sequence is the disjoint union of the powers of 2 (A000079) and the sequence A289274. %H A289275 Giovanni Resta, <a href="/A289275/b289275.txt">Table of n, a(n) for n = 1..58</a> %t A289275 Select[Range[10^5], IntegerQ@ Sqrt[2 #^2 - DivisorSigma[1, #^2]] &] (* _Michael De Vlieger_, Jul 04 2017 *) %o A289275 (PARI) isok(n) = issquare(2*n^2 - sigma(n^2)); \\ _Michel Marcus_, Jul 01 2017 %Y A289275 Disjoint union of the sequences A000079 and A289274. %Y A289275 Square roots of deficiencies of squares is A288145. %K A289275 nonn %O A289275 1,2 %A A289275 _Jens Voß_, Jun 30 2017 %E A289275 a(35)-a(38) from _Giovanni Resta_, Jul 27 2017