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 A056305 #10 Aug 22 2017 20:53:08 %S A056305 0,0,0,1,2,13,50,220,866,3435,13250,51061,194810,742601,2823764, %T A056305 10738660,40843370,155493872,592614050,2261622287,8643289484, %U A056305 33080907357,126797503250,486710920300,1870851589552 %N A056305 Number of primitive (period n) n-bead necklace structures using exactly four different colored beads. %C A056305 Turning over the necklace is not allowed. Colors may be permuted without changing the necklace structure. %D A056305 M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2] %F A056305 Sum mu(d)*A056297(n/d) where d|n. Alternatively, A056300(n)-A002075(n).. %Y A056305 Column 4 of A107424. %Y A056305 Cf. A056289. %K A056305 nonn %O A056305 1,5 %A A056305 _Marks R. Nester_