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A100796
Equivalence class of numerical representation of n. See Comments for definition.
0
0, 1, 1, 1, 4, 1, 6, 1, 8, 6, 10, 11, 11, 11, 14, 11, 16, 11, 18, 16, 10, 11, 11, 11, 14, 11, 16, 11, 18, 16, 10, 11, 11, 11, 14, 11, 16, 11, 18, 16, 40, 14, 14, 14, 11, 14, 46, 14, 48, 46, 10, 11, 11, 11, 14, 11, 16, 11, 18, 16, 60, 16, 16, 16, 46, 16, 66, 16, 68, 66, 10, 11, 11
OFFSET
0,5
COMMENTS
The 10 digits 0,1,...,9 (written in a sans serif font) are covered by 5 equivalence classes: C_0 = {0}, a circle; C_1 = {1, 2, 3, 5, 7}, a line segment; C_4 = {4}, a circle with a point to which is glued two line segments; C_6 = {6, 9}, a circle with a point to which is glued a line segment; C_8 = {8}, a figure eight.
This is different from the topological classification, which would classify the digits according to their genus: {1,2,3,5,7}, {0,4,6,9} and {8}.
LINKS
Eric Weisstein's World of Mathematics, Figure Eight.
Eric Weisstein's World of Mathematics, Circle.
CROSSREFS
Sequence in context: A136706 A326478 A324118 * A354433 A005451 A135683
KEYWORD
nonn,less
AUTHOR
Jonathan Vos Post, Jun 06 2007
EXTENSIONS
Edited by N. J. A. Sloane, Oct 07 2007
More terms from David Wasserman, Mar 04 2008
STATUS
approved