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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 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=0..72.

Eric Weisstein's World of Mathematics, Figure Eight.

Eric Weisstein's World of Mathematics, Circle.

CROSSREFS

Sequence in context: A136706 A326478 A324118 * A005451 A135683 A113520

Adjacent sequences:  A100793 A100794 A100795 * A100797 A100798 A100799

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

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Last modified May 23 18:08 EDT 2022. Contains 353993 sequences. (Running on oeis4.)