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 A009927 #41 Apr 10 2018 08:26:36 %S A009927 1,12,50,120,218,344,546,728,902,1212,1526,1784,2154,2552,2954,3432, %T A009927 3854,4340,4998,5504,6002,6768,7442,8024,8814,9572,10334,11232,11978, %U A009927 12824,13938,14768,15590,16812,17846,18752,19962,21080,22202,23520 %N A009927 Coordination sequence for Cr3Si, Si position. %D A009927 Gmelin Handbook of Inorg. and Organomet. Chem., 8th Ed., 1994, TYPIX search code (223) cP8. %H A009927 R. W. Grosse-Kunstleve, <a href="/A009927/b009927.txt">Table of n, a(n) for n = 0..1000</a> %H A009927 V. A. Blatov, A. P. Shevchenko, D. M. Proserpio, <a href="http://pubs.acs.org/doi/pdf/10.1021/cg500498k">Applied Topological Analysis of Crystal Structures with the Program Package ToposPro</a>, Cryst. Growth Des. 2014, 14, 3576-3586. See Table I. %H A009927 R. W. Grosse-Kunstleve, <a href="/A005897/a005897.html">Coordination Sequences and Encyclopedia of Integer Sequences</a> %H A009927 R. W. Grosse-Kunstleve, G. O. Brunner and N. J. A. Sloane, <a href="http://neilsloane.com/doc/ac96cs/">Algebraic Description of Coordination Sequences and Exact Topological Densities for Zeolites</a>, Acta Cryst., A52 (1996), pp. <a href="http://dx.doi.org/10.1107/S0108767396007519">879-889</a>. %F A009927 G.f.: (1+12*x+51*x^2+130*x^3+243*x^4+350*x^5+450*x^6+418*x^7 +327*x^8+182*x^9+51*x^10+16*x^11-7*x^12+8*x^13+12*x^14)/ ((1+x)*(1+x^2)^2*(1+x+x^2)^2*(1-x)^3). - _Robert Israel_, Dec 18 2015 %F A009927 Empirical: a(n) = (1903/72) + (3/8)*(-1)^n + 19*KroneckerDelta[n,0] - 8*KroneckerDelta[n,1] - 12*KroneckerDelta[n,2] + ((n+1)/12)*(187*n-273) - (32*sqrt(3)/27)*((13/2)*cos((4n+1)*Pi/6) + sin(2n*Pi/3)) - (3*sqrt(26)/2)*(-1)^n*cos(n*Pi/2 + arctan(1/5)) - (3/4)*i^n*(1+(-1)^n)*(n+2). - _G. C. Greubel_, Dec 18 2015 %F A009927 G.f.: (1 + 12*x + 50*x^2 + 118*x^3 + 192*x^4 + 220*x^5 + 207*x^6 + 68*x^7-123*x^8-236*x^9-276*x^10-166*x^11-58*x^12-8*x^13 + 19*x^14-8*x^15-12*x^16) / (1-x^3)^2 / (1-x^4)^2. - _Sean A. Irvine_, Mar 15 2018 %K A009927 nonn %O A009927 0,2 %A A009927 _Ralf W. Grosse-Kunstleve_