OFFSET
1,1
REFERENCES
Problem #139, An Enumeration Problem" by David L. Silverman, J. Rec. Math., 8 (1976), 323-327.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved