OFFSET
0
COMMENTS
Decimal expansion of 900000001/9000000000. - Elmo R. Oliveira, May 29 2024
LINKS
FORMULA
a(0)=1; for 0 < n < 9 a(n)=0; for n >= 9, a(n)=1.
Inverse Euler transformation of A185329.
G.f.: (x^9-x+1)/(1-x). - Elmo R. Oliveira, May 29 2024
EXAMPLE
The null graph is vacuously 2-regular and, being acyclic, has infinite girth.
There are no 2-regular simple graphs with 1 or 2 vertices.
The n-cycle has girth n.
CROSSREFS
2-regular simple graphs with girth at least 9: this sequence (connected), A185229 (disconnected), A185329 (not necessarily connected).
Connected k-regular simple graphs with girth at least 9: A186729 (all k), A186719 (triangular array), this sequence (k=2).
Connected 2-regular simple graphs with girth at least g: A179184 (g=3), A185114 (g=4), A185115 (g=5), A185116 (g=6), A185117 (g=7), A185118 (g=8), A185119 (g=9).
KEYWORD
nonn,easy
AUTHOR
Jason Kimberley, Jan 28 2011
STATUS
approved