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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A182797 Square array A(n,k), n>=1, k>=1, read by antidiagonals: A(n,k) is the number of n-colorings of the Triangle Graph of order k. 22
 1, 0, 2, 0, 0, 3, 0, 0, 6, 4, 0, 0, 6, 24, 5, 0, 0, 6, 192, 60, 6, 0, 0, 6, 2112, 1620, 120, 7, 0, 0, 6, 32640, 98820, 7680, 210, 8, 0, 0, 6, 718080, 13638780, 1574400, 26250, 336, 9, 0, 0, 6, 22665216, 4260983940, 1034019840, 13676250, 72576, 504, 10 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The Triangle Graph of order k has k rows with i vertices in row i. Each vertex is connected to the neighbors in the same row and up to two vertices in each of the neighboring rows. The Graph has A000217(k) vertices and 3*A000217(k-1) edges altogether. LINKS Eric Weisstein's World of Mathematics, Triangle Graph Wikipedia, Chromatic polynomial EXAMPLE Square array A(n,k) begins:   1,   0,    0,       0,          0,             0,  ...   2,   0,    0,       0,          0,             0,  ...   3,   6,    6,       6,          6,             6,  ...   4,  24,  192,    2112,      32640,        718080,  ...   5,  60, 1620,   98820,   13638780,    4260983940,  ...   6, 120, 7680, 1574400, 1034019840, 2175789895680,  ... CROSSREFS Columns k=1-11 give: A000027, A007531, A182788, A182789, A182790, A182791, A182792, A182793, A182794, A182795, A182796. Rows n=1-10 give: A000007(k-1), A000038(k-1), A040006(k-1), A182798, A153467*4, A153468*5, A153469*6, A153470*7, A153471*8, A153472*9, A153473*10. Cf. A000217, A193283. Sequence in context: A136274 A290976 A114699 * A212163 A212195 A228926 Adjacent sequences:  A182794 A182795 A182796 * A182798 A182799 A182800 KEYWORD nonn,tabl AUTHOR Alois P. Heinz, Dec 02 2010 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 December 1 16:44 EST 2021. Contains 349430 sequences. (Running on oeis4.)