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 A134515 #17 Aug 21 2017 03:11:37
%S A134515 1,0,0,10,15,168,1008,8244,73125,726440,7939008,94744494,1225760627,
%T A134515 17088219120,255365758560,4072255216296,69021889788969,
%U A134515 1239055874931312,23484788783212480,468656477004105810,9821896865573503095
%N A134515 Third column (k=2) of triangle A134832 (circular succession numbers).
%C A134515 a(n) enumerates circular permutations of {1,2,...,n+2} with exactly two successor pairs (i,i+1). Due to cyclicity also (n+2,1) is a successor pair.
%D A134515 Ch. A. Charalambides, Enumerative Combinatorics, Chapman & Hall/CRC, Boca Raton, Florida, 2002, p. 183, eq. (5.15), for k=2.
%H A134515 Bhadrachalam Chitturi and Krishnaveni K S, <a href="https://arxiv.org/abs/1601.04469">Adjacencies in Permutations</a>, arXiv preprint arXiv:1601.04469 [cs.DM], 2016.
%F A134515 E.g.f.: (d^2/dx^2) (x^2/2!)*(1-log(1-x))/e^x.
%F A134515 a(n) = (((n+2)*(n+1))/2)*A000757(n), n>=0.
%e A134515 a(2)=0 because the 4!/4 = 6 circular permutations of n=4 elements (1,2,3,4), (1,4,3,2), (1,3,4,2),(1,2,4,3), (1,4,2,3) and (1,3,2,4) have 4,0,1,1,1 and 1 successor pair, respectively.
%Y A134515 Cf. A135799 (column k=1).
%K A134515 nonn,easy
%O A134515 0,4
%A A134515 _Wolfdieter Lang_, Jan 21 2008, Feb 22 2008