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 A005724 M3148 #21 Oct 12 2017 19:24:11 %S A005724 3,40,546,7728,112035,1650792,24608948,370084832,5603730876, %T A005724 85316186400,1304770191802,20029132137840,308437355259930, %U A005724 4762695514958640,73716196036213800,1143325208566357440,17765127399780725316,276484586847524844768,4309270265307160983144 %N A005724 Quadrinomial coefficients. %D A005724 L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 78. %D A005724 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A005724 R. K. Guy, <a href="/A005712/a005712.pdf">Letter to N. J. A. Sloane, 1987</a> %F A005724 a(n) = A008287(2 * n, 3 * n - 1). - _Sean A. Irvine_, Aug 15 2016 %p A005724 seq(coeff((1+x+x^2+x^3)^(2*n),x,3*n-1), n=1..30); # _Robert Israel_, Aug 15 2016 %Y A005724 Cf. A008287. %K A005724 nonn %O A005724 1,1 %A A005724 _N. J. A. Sloane_ %E A005724 Offset changed by _Robert Israel_, Aug 15 2016