%I M3001 N1216 #23 May 08 2018 15:11:53
%S 3,15,105,315,6930,18018,90090,218790,2078505,4849845,22309287,
%T 50702925,1825305300,4071834900,18032411700,39671305740,347123925225,
%U 755505013725,3273855059475,7064634602025,121511715154830
%N Coefficients of Legendre polynomials.
%D M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 798.
%D G. Prévost, Tables de Fonctions Sphériques. Gauthier-Villars, Paris, 1933, pp. 156-157.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H M. Abramowitz and I. A. Stegun, eds., <a href="http://www.convertit.com/Go/ConvertIt/Reference/AMS55.ASP">Handbook of Mathematical Functions</a>, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
%H M. Janjic, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL12/Janjic/janjic22.html">Some classes of numbers and derivatives</a>, JIS 12 (2009) 09.8.3
%o (PARI) a(n)=if(n<0,0,polcoeff(pollegendre(n+4),n)*2^valuation((n\2*2+4)!,2))
%Y Cf. A001790, A001800, A008316.
%Y Bisection of A004733.
%Y Diagonal 3 of triangle A100258.
%K nonn
%O 0,1
%A _N. J. A. Sloane_
%E More terms from _Michael Somos_, Oct 25 2002