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 A260020 #13 Nov 08 2017 22:24:20 %S A260020 2,3,8,9,15,26,39,45,74,104,111,117,122,128,146,175,183,195,219,296, %T A260020 314,333,357,386,471,488,549,554,555,579,584,585,608,626,646,657,794, %U A260020 831,842,914,915,939,962,1071,1082,1095,1191,1226,1256,1263,1292,1322 %N A260020 Numbers n such that 2*phi(n) = phi(2*sigma(n)). %H A260020 Reinhard Zumkeller, <a href="/A260020/b260020.txt">Table of n, a(n) for n = 1..10000</a> %H A260020 S. W. Golomb, <a href="/A006872/a006872_1.pdf">Equality among number-theoretic functions</a>, Unpublished manuscript. (Annotated scanned copy) %o A260020 (Haskell) %o A260020 a260020 n = a260020_list !! (n-1) %o A260020 a260020_list = filter %o A260020 (\x -> 2 * a000010' x == a000010' (2 * a000203' x)) [1..] %o A260020 -- _Reinhard Zumkeller_, Jul 14 2015 %Y A260020 Cf. A006872. %Y A260020 Cf. A000010, A000203. %K A260020 nonn %O A260020 1,1 %A A260020 _N. J. A. Sloane_, Jul 14 2015