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 A049449 #14 Mar 07 2020 01:14:16 %S A049449 0,1,2,3,6,4,10,15,12,5,14,24,21,28,40,35,20,6,18,33,30,44,65,60,36, %T A049449 45,84,104,77,70,88,63,30,7,22,42,39,60,90,85,52,70,133,168,126,119, %U A049449 152,112,55,66,144,209,170,198,273,228,126,117,204,234,165,130,154,99,42,8 %N A049449 Product of numerator and denominator of fractions in Farey tree A007305/A007306. %C A049449 Sum of reciprocals of each row (n > 1) equals 1/2. E.g., 1/3 + 1/6, 1/4 + 1/10 + 1/15 + 1/12 and so on. The link to cut-the-knot gives credit to Pierre Lamothe for this observation. - _Joshua Zucker_, May 11 2006 %D A049449 J. C. Lagarias, Number Theory and Dynamical Systems, pp. 35-72 of S. A. Burr, ed., The Unreasonable Effectiveness of Number Theory, Proc. Sympos. Appl. Math., 46 (1992). Amer. Math. Soc. %H A049449 Ivan Neretin, <a href="/A049449/b049449.txt">Table of n, a(n) for n = 0..4096</a> %H A049449 Alexander Bogomolny, <a href="http://www.cut-the-knot.org/blue/Stern.shtml">Cut-the-knot on Stern-Brocot trees</a> %F A049449 A007305*A007306. %Y A049449 See comment in A119272. %K A049449 nonn,easy,tabf %O A049449 0,3 %A A049449 _N. J. A. Sloane_ %E A049449 More terms from Megan Wawro (s1095813(AT)cedarville.edu) %E A049449 More terms from _Joshua Zucker_, May 11 2006