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 A005870 M2516 #24 Jul 08 2025 16:37:31 %S A005870 0,3,6,8,9,11,12,15,17,18,19,20,21,22,25,27,29,30,31,32,33,34,35,36, %T A005870 37,39,41,43,44,45,46,47,48,49,51,53,54,55,56,57,59,61,63,65,66,67,68, %U A005870 69,70,71,72,75 %N A005870 Numbers represented by hexagonal close-packing. %C A005870 Numbers n such that A004012(n) != 0. - _Sean A. Irvine_, Sep 23 2016 %D A005870 J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 114. %D A005870 S. E. Thiel, Generating Functions for Fibonomial Coefficients and Fibonacci Products, http://stuartthiel.homestead.com/files/fibonacci/THIEL_fibonomial_coefficients_rev110612.pdf [Broken link?] %D A005870 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %Y A005870 Cf. A004012. %K A005870 easy,nonn %O A005870 1,2 %A A005870 _N. J. A. Sloane_