OFFSET
1,2
EXAMPLE
There are 3 ways to join two cells of the cubic grid at faces, edges, or vertices, so a(2) = 3.
CROSSREFS
KEYWORD
nonn,nice,more,hard
AUTHOR
George Sicherman, Apr 27 2016
EXTENSIONS
a(8) and a(9) from Joerg Arndt and Márk Péter Légrádi, May 28 2023
STATUS
approved