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 A011947 #15 Jul 08 2025 02:43:05 %S A011947 1,1,3,7,14,31,63,123,255,511,1015,2047,4092 %N A011947 Number of Barlow packings with group P63/mmc(O) that repeat after 4n+2 layers. %C A011947 Apparently identical to A129629. %D A011947 T. J. McLarnan, The numbers of polytypes ..., Zeits. Krist. 155, 269-291 (1981). %F A011947 Conjecture: a(n) = A045683(2n+1). - _R. J. Mathar_, Apr 15 2024 %K A011947 nonn,easy %O A011947 0,3 %A A011947 _N. J. A. Sloane_