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 A005960 M2747 #34 Jan 10 2018 09:05:10 %S A005960 1,3,8,23,69,208,636,1963,6099,19059,59836,188576,596252,1890548, %T A005960 6008908,19139155,61074583,195217253,624913284,2003090071,6428430129, %U A005960 20653101216,66420162952,213802390264,688796847976,2220789746752,7165331870036 %N A005960 Number of acyclic disubstituted alkanes with n carbon atoms and distinct substituents. %C A005960 Acyclic alkanes of the form C_nH_mXY with X != Y. For X = Y see A005961. - _Sean A. Irvine_, Nov 12 2016 %D A005960 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A005960 R. C. Read, <a href="/A000598/a000598.pdf">The Enumeration of Acyclic Chemical Compounds</a>, pp. 25-61 of A. T. Balaban, ed., Chemical Applications of Graph Theory, Ac. Press, 1976. [Annotated scanned copy] See p. 44. %F A005960 G.f.: 1/(1-x*B(x)^2) where B(x) is the g.f. for A000625. - _Sean A. Irvine_, Nov 12 2016 %t A005960 terms = 27; (* B = g.f. for A000625 *) B[_] = 0; Do[B[x_] = 1 + x*((B[x]^3 + 2*B[x^3])/3) + O[x]^(terms + 1) // Normal, terms + 1]; %t A005960 A[x_] = 1/(1 - x*B[x]^2) + O[x]^(terms + 1); %t A005960 CoefficientList[A[x], x] // Rest (* _Jean-François Alcover_, Jan 10 2018 *) %Y A005960 Cf. A193418. %K A005960 nonn %O A005960 1,2 %A A005960 _N. J. A. Sloane_ %E A005960 More terms and title improved by _Sean A. Irvine_, Nov 12 2016