%I A002803 M4980 N2140
%S A002803 1,15,140,1050,6930,42042,240240,1312740,6928350,35565530,178474296,
%T A002803 878850700,4259045700,20359174500,96172862400,449608131720,
%U A002803 2082743551350,9569730173850,43651400793000,197809768856700
%N A002803 (2n+4)!/(4!n!(n+1)!).
%D A002803 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A002803 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002803 C. Jordan, Calculus of Finite Differences. Budapest, 1939, p. 449.
%D A002803 Walsh, T. R. S.; Lehman, A. B.; Counting rooted maps by genus. III: Nonseparable 
               maps. J. Combinatorial Theory Ser. B 18 (1975), 222-259.
%p A002803 seq(binomial(2*i,i)*binomial(i,i-2)*i/12, i=2..21); - Zerinvary Lajos 
               (zerinvarylajos(AT)yahoo.com), Jan 06 2007
%t A002803 a[n_]:=(2*n+4)!/(4!*n!*(n+1)!); [From Vladimir Orlovsky (4vladimir(AT)gmail.com), 
               Dec 13 2008]
%Y A002803 Sequence in context: A027802 A133716 A035330 this_sequence A056281 A000481 
               A055903
%Y A002803 Adjacent sequences: A002800 A002801 A002802 this_sequence A002804 A002805 
               A002806
%K A002803 nonn,easy
%O A002803 0,2
%A A002803 N. J. A. Sloane (njas(AT)research.att.com).
%E A002803 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 17 2003