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 A000564 M5099 N2208 #38 Sep 08 2022 08:44:28
%S A000564 20,371,2588,11097,35645,94457,218124,454220,872648,1571715,2684936,
%T A000564 4388567,6909867,10536089,15624200,22611330,32025950,44499779,
%U A000564 60780420,81744725,108412889,141963273,183747956,235309016,298395540
%N A000564 Number of discordant permutations.
%D A000564 J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
%D A000564 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A000564 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A000564 Simon Plouffe, <a href="https://arxiv.org/abs/0911.4975">Approximations de séries génératrices et quelques conjectures</a>, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
%H A000564 Simon Plouffe, <a href="/A000051/a000051_2.pdf">1031 Generating Functions</a>, Appendix to Thesis, Montreal, 1992
%H A000564 J. Riordan, <a href="/A000211/a000211.pdf">Discordant permutations</a>, Scripta Math., 20 (1954), 14-23. [Annotated scanned copy]
%H A000564 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21, 35,-35,21,-7,1).
%F A000564 From Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001: (Start)
%F A000564 G.f.: -x^6(2x^7 - 4x^6 + 36x^5 - 29x^4 - 72x^3 - 411x^2 - 231x - 20) / ((1 - x)^7).
%F A000564 a(n) = 81/80n^6 - 405/16n^5 + 4113/16n^4 - 21267/16n^3 + 140357/40n^2 - 7587/2n, n>6. (End)
%p A000564 rr := n - >81/80*n^6 - 405/16*n^5 + 4113/16*n^4 - 21267/16*n^3 + 140357/40*n^2 - 7587/2*n; seq(rr(n), n=7..40); # Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001
%p A000564 A000564:=(-20-231*z-411*z**2-72*z**3-29*z**4+36*z**5-4*z**6+2*z**7)/(z-1)**7; # conjectured by _Simon Plouffe_ in his 1992 dissertation
%t A000564 Join[{20}, LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {371, 2588, 11097, 35645, 94457, 218124, 454220}, 30]] (* _Jean-François Alcover_, Feb 10 2016 *)
%o A000564 (Magma) [20] cat [81/80*n^6-405/16*n^5+4113/16*n^4-21267/16*n^3+140357/40*n^2 - 7587/2*n: n in [7..45]]; // _Vincenzo Librandi_, Feb 10 2016
%K A000564 nonn,easy
%O A000564 6,1
%A A000564 _N. J. A. Sloane_
%E A000564 More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001