OFFSET
1,1
REFERENCES
Martin Gardner, More Mathematical Puzzles and Diversions, page 63, "a network tracing puzzle".
EXAMPLE
a(1)=3 since you have to make two turns to trace the triangle and one to cover the circular part of the network.
From Sean A. Irvine, Feb 07 2023: (Start)
a(3)=10, there are 9 triangles:
A
/ \
B---C
/ \ / \
D---E---F
/ \ / \ / \
G---H---I---J
Start on the circle (which passes through A, G, J, but is not shown in this picture), then trace the complete figure with A-J-G-B-I-F-D-H-C-B-A for a total of 10 turns. Note other paths achieving the same minimum number of turns are possible. (End)
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Brian Wallace (wallacebrianedward(AT)yahoo.co.uk), May 22 2001
EXTENSIONS
a(3) onward corrected by Sean A. Irvine, Feb 07 2023
STATUS
approved