%I A005348 M1435
%S A005348 1,2,5,13,33,81,193,449,1089,2673,6561,15633,37249,88209,216513,531441,
%T A005348 1266273,3017169,7189057,17537553,43046721,102568113,244390689,582313617
%N A005348 Number of ways to add n ordinals.
%D A005348 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005348 Wakulicz, A. Sur la somme d'un nombre fini de nombres ordinaux. Fund. 
               Math. 36 (1949), 254-266; 38 (1951), 239.
%D A005348 P. Erdos, Some remarks on set theory, Proc. Am. Math. Soc. 1 (1950) 127-141.
%D A005348 W. Sierpinski, Cardinal and Ordinal Numbers, 2nd ed. p 275.
%D A005348 R. K. Guy, The second strong law of small numbers. Math. Mag. 63 (1990), 
               no. 1, 3-20.
%H A005348 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               OrdinalNumber.html">Link to a section of The World of Mathematics.</
               a>
%H A005348 A. Wakulicz, <a href="http://matwbn.icm.edu.pl/ksiazki/fm/fm36/fm3626.pdf">
               Sur la somme d'un nombre fini de nombres ordinaux</a>, Fund. Math. 
               36 (1949), 254-266.
%F A005348 a(n)=81*a(n-5) for n >= 21.
%Y A005348 Sequence in context: A001659 A088921 A005183 this_sequence A067676 A116703 
               A116724
%Y A005348 Adjacent sequences: A005345 A005346 A005347 this_sequence A005349 A005350 
               A005351
%K A005348 nonn,easy
%O A005348 1,2
%A A005348 N. J. A. Sloane (njas(AT)research.att.com), R. K. Guy, Bill Sands and 
               Tommy Kucera.