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 A056417 #6 Aug 22 2017 20:53:11 %S A056417 0,0,0,3,12,136,204,1437,3520,20700,31956,317513,390364,2973536, %T A056417 8504720,32471391,61276740,622088400,790198476,6798297447,17290258088, %U A056417 79394956608,138325216092,1460955482487 %N A056417 Number of step cyclic shifted sequences using exactly four different symbols. %C A056417 See A056371 for an explanation of step shifts. Under step cyclic shifts, abcde, bdace, bcdea, cdeab and daceb etc. are equivalent. %D A056417 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 A056417 A056412(n)-4*A056411(n)+6*A002729(n)-4. %Y A056417 Cf. A056412. %K A056417 nonn %O A056417 1,4 %A A056417 _Marks R. Nester_