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 A230554 #14 Oct 28 2013 13:30:20 %S A230554 1,1,2,4,9,21,51,126,321,820,2160,5654,15272,40758,112280,304471, %T A230554 852164,2341980,6640755,18460066,52915999 %N A230554 Number of involutions avoiding the pattern 1324. %H A230554 Miklós Bóna, Cheyne Homberger, Jay Pantone, and Vince Vatter, <a href="http://arxiv.org/abs/1310.7003">Pattern-avoiding involutions: exact and asymptotic enumeration</a>, arxiv:1310.7003, 2013. %e A230554 Of the 26 involutions of length 5, only 21435, 13254, 13245, 14325, and 12435 contain the pattern 1324, so a(5) = 21. %Y A230554 Cf. A000085, A001006, A121704, A230551-A230556. %K A230554 nonn %O A230554 0,3 %A A230554 _Cheyne Homberger_, Oct 23 2013