%I A006736 M3597
%S A006736 0,4,24,104,384,1284,4012,11924,34100,94584,255852,677850,1764482,
%T A006736 4523924,11447870,28636218,70907326,173991368,423469988,1023162920,
%U A006736 2455645268,5858183260,13898041838,32804047708,77067740230
%N A006736 Series for first parallel moment of hexagonal lattice.
%C A006736 The hexagonal lattice is the familiar 2-dimensional lattice in which 
               each point has 6 neighbors. This is sometimes called the triangular 
               lattice.
%D A006736 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A006736 J. W. Essam, A. J. Guttmann and K. De'Bell, On two-dimensional directed 
               percolation, J. Phys. A 21 (1988), 3815-3832.
%D A006736 Jensen, Iwan; Guttmann, Anthony J.; Series expansions of the percolation 
               probability for directed square and honeycomb lattices. J. Phys. 
               A 28 (1995), no. 17, 4813-4833.
%H A006736 I. Jensen, <a href="b006736.txt">Table of n, a(n) for n = 0..90</a> (from 
               link below)
%H A006736 I. Jensen, <a href="http://www.ms.unimelb.edu.au/~iwan/dirperc/series/
               triabond_t1.ser">More terms</a>
%H A006736 G. Nebe and N. J. A. Sloane, <a href="http://www.research.att.com/~njas/
               lattices/A2.html">Home page for hexagonal (or triangular) lattice 
               A2</a>
%Y A006736 Cf. A006803, A006809, A006737.
%Y A006736 Sequence in context: A052462 A048806 A043009 this_sequence A165752 A166036 
               A120908
%Y A006736 Adjacent sequences: A006733 A006734 A006735 this_sequence A006737 A006738 
               A006739
%K A006736 nonn
%O A006736 0,2
%A A006736 N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)