The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A212209 Square array A(n,k), n>=1, k>=1, read by antidiagonals: A(n,k) is the number of n-colorings of the square diagonal grid graph DG_(k,k). 19
 1, 0, 2, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0, 24, 5, 0, 0, 0, 72, 120, 6, 0, 0, 0, 168, 6720, 360, 7, 0, 0, 0, 360, 935040, 126360, 840, 8, 0, 0, 0, 744, 325061760, 265035240, 1128960, 1680, 9, 0, 0, 0, 1512, 283192323840, 3322711053720, 17160407040, 6510000, 3024, 10 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The square diagonal grid graph DG_(n,n) has n^2 = A000290(n) vertices and 2*(n-1)*(2*n-1) = A002943(n-1) edges; see A212208 for example. The chromatic polynomial of DG_(n,n) has n^2+1 = A002522(n) coefficients. This graph is also called the king graph. - Andrew Howroyd, Jun 25 2017 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..153 Eric Weisstein's World of Mathematics, King Graph Wikipedia, Chromatic Polynomial EXAMPLE Square array A(n,k) begins:   1,   0,       0,           0,                0, ...   2,   0,       0,           0,                0, ...   3,   0,       0,           0,                0, ...   4,  24,      72,         168,              360, ...   5, 120,    6720,      935040,        325061760, ...   6, 360,  126360,   265035240,    3322711053720, ...   7, 840, 1128960, 17160407040, 2949948395735040, ... CROSSREFS Columns 1-5 give: A000027, A052762 = 24*A000332, 24*A068250, 24*A068251, 24*A068252. Rows n=1-16 give: A000007, A000038, 3*A000007, 4*A068293, 5*A068294, 6*A068295, 7*A068296, 8*A068297, 9*A068298, 10*A068299, 11*A068300, 12*A068301, 13*A068302, 14*A068303, 15*A068304, 16*A068305. Cf. A000290, A002943, A212208, A208021. Sequence in context: A140579 A132681 A127648 * A259481 A132825 A259480 Adjacent sequences:  A212206 A212207 A212208 * A212210 A212211 A212212 KEYWORD nonn,tabl AUTHOR Alois P. Heinz, May 04 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 21 19:57 EDT 2020. Contains 337273 sequences. (Running on oeis4.)