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 A212191 #34 Sep 22 2022 01:49:25 %S A212191 5,7,9,10,14,17,18,20,23,28,33,34,36,40,46,56,65,66,68,72,80,92,112, %T A212191 129,130,132,136,144,160,184,224,257,258,260,264,272,288,320,368,448, %U A212191 513,514,516,520,528,544,576,640,736,896,1025,1026,1028,1032,1040 %N A212191 Numbers whose squares are the sum of exactly three distinct powers of 2. %C A212191 The finite sequence 5, 7, 9, 10, 14, 17 arises in the following context: squarefree circular words over the ternary alphabet exist for all lengths n except for 5, 7, 9, 10, 14, 17. See Currie (2002), Shur (2010). - _N. J. A. Sloane_, May 04 2013 %H A212191 Giovanni Resta, <a href="/A212191/b212191.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Reinhard Zumkeller) %H A212191 J. D. Currie, <a href="https://doi.org/10.37236/1671">There are ternary circular square-free words of length n for n >= 18</a>, Elect. J. Combinatorics 9 (2002), Note #N10. %H A212191 James D. Currie, and Jesse T. Johnson, <a href="https://arxiv.org/abs/2005.06235">There are level ternary circular square-free words of length n for n != 5,7,9,10,14,17</a>, arXiv:2005.06235 [math.CO], 2020. %H A212191 Arseny M. Shur, <a href="https://doi.org/10.37236/412">On Ternary Square-free Circular Words</a>, Electronic J. Combin., Volume 17 (2010), Research Paper #R140. %F A212191 a(n)^2 = A212190(n). %t A212191 Select[Range[1, 1000], Total[IntegerDigits[#^2, 2]] == 3 &] (* _T. D. Noe_, Dec 07 2012 *) %o A212191 (Haskell) %o A212191 a212191 n = a212191_list !! (n-1) %o A212191 a212191_list = map a000196 a212190_list %Y A212191 Cf. A000196, A005009 (subsequence). %K A212191 nonn %O A212191 1,1 %A A212191 _Reinhard Zumkeller_, May 03 2012