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 A121180 #12 Jul 29 2023 14:34:13
%S A121180 0,0,0,1,1,5,6,26,32,133,176,708,952,3861,5302,21604,29960
%N A121180 Alkane systems (see Cyvin reference for precise definition).
%C A121180 Appears to be A047774 without every third term (all omitted terms are zeros). - _Andrey Zabolotskiy_, Jul 29 2023
%H A121180 S. J. Cyvin, Jianji Wang, J. Brunvoll, Shiming Cao, Ying Li, B. N. Cyvin, and Yugang Wang, <a href="https://doi.org/10.1016/S0022-2860(97)00025-2">Staggered conformers of alkanes: complete solution of the enumeration problem</a>, J. Molec. Struct. 413-414 (1997), 227-239. See Table 5, column C_2.
%Y A121180 Cf. other columns of Cyvin et al.'s Table 5: A027610 (spectral isomers), A007173 (stereoisomers), A047775 (C_s), A047772 (C_i), A047774 (C_3, apparently), A047767 (C_{2h}), A047761 (C_{2v}), A047773 (C_{3v}, apparently).
%Y A121180 Cf. A121181, A121189.
%K A121180 nonn,more
%O A121180 1,6
%A A121180 _N. J. A. Sloane_, Aug 17 2006