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!)
 A261834 Number of n-step adjacent expansions on the hexagonal (honeycomb) lattice. Holes allowed. 1
 1, 6, 48, 468, 5328, 68928, 994464, 15781920, 272594160, 5081825664 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Initially only one cell C[0] is occupied on the lattice. Then, for each i of (1..n), C[i] is chosen among the free cells adjacent to at least one of (C[0],..,C[i-1]). a(n) is the number of distinct (C[1],..,C[n]). LINKS Francois Alcover, tree EXAMPLE a(1) = 6 because a point has 6 neighbors on the hex grid. a(2) = 48 = a(1) * 8 because a two-cell group has 8 free neighbors. CROSSREFS Cf. A007846 (same principle but on the rectangular lattice). Cf. A001334. Sequence in context: A085457 A188911 A319292 * A226740 A244509 A105627 Adjacent sequences:  A261831 A261832 A261833 * A261835 A261836 A261837 KEYWORD nonn,more AUTHOR Francois Alcover, Mar 24 2016 EXTENSIONS More terms from Francois Alcover, Apr 29 2016 Rephrasing and culling comments from Francois Alcover, Apr 29 2016 Added crossref to A007846 from Francois Alcover, May 01 2016 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 May 26 22:58 EDT 2020. Contains 334634 sequences. (Running on oeis4.)