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 A006670 M0252 #19 Jul 08 2025 16:52:12
%S A006670 1,1,2,2,3,3,3,4,4,4,5,5,5,5,5,5,6,6,6,6,7,7,7,7,7,7,7,7,7,8,8,8,8,8,
%T A006670 9,9,9,9,9,9,9,9,9,9,9,9,10,10,10,10,10,10,11,11,11,11,11,11,11,11,11,
%U A006670 11,11,11,11,11,11,12,12,12,12,12,12,12
%N A006670 Edge-distinguishing chromatic number of path with n nodes.
%C A006670 This is not the ordinary chromatic number, which is 2 for paths and 2 or 3 for cycles (A006671). - _Keith Briggs_, Feb 22 2006
%C A006670 The minimum number of colors which can be assigned to the vertices of the path such that each edge e=uv in the path is assigned a different "color" {c(u),c(v)}. - _Sean A. Irvine_, Jun 14 2017
%D A006670 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A006670 K. Al-Wahabi, R. Bari, F. Harary and D. Ullman, <a href="https://doi.org/10.1016/S0167-5060(08)70446-1">The edge-distinguishing chromatic number of paths and cycles</a>, pp. 17-22 of Graph Theory in Memory of G. A. Dirac (Sandbjerg, 1985). Edited by L. D. Andersen et al., Annals of Discrete Mathematics, 41. North-Holland Publishing Co., Amsterdam-New York, 1989.
%F A006670 For n > 2, if either r is odd, and r^2 - 2*r + 5 < 2*n <= r^2 + r + 2, or r is even, and r^2 - r + 2 < 2 * n <= r^2 + 2, then a(n) = r [From Al-Wahabi, et al.]. - _Sean A. Irvine_, Jun 14 2017
%K A006670 nonn
%O A006670 1,3
%A A006670 _N. J. A. Sloane_
%E A006670 More terms and title improved by _Sean A. Irvine_, Jun 14 2017