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A248571 Number of connected irreducible digital images of n points up to homotopy equivalence. 3
1, 0, 0, 0, 1, 1, 3, 28, 547 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

COMMENTS

"Irreducible" means not homotopy equivalent to any digital image of fewer points. The terms are nonzero for all n>4, and are believed to be strictly increasing for n>6.

LINKS

Table of n, a(n) for n=1..9.

J. Haarmann, M. Murphy, C. Peters, and P. C. Staecker, Homotopy equivalence of finite digital images, arXiv:1408.2584 [math.GN], 2014.

P. C. Staecker, Some enumerations of binary digital images, arXiv:1502.06236 [math.CO], 2015.

CROSSREFS

Sequence in context: A192559 A161971 A156315 * A062497 A056066 A174483

Adjacent sequences:  A248568 A248569 A248570 * A248572 A248573 A248574

KEYWORD

nonn,more,hard

AUTHOR

P. Christopher Staecker, Oct 13 2014

EXTENSIONS

a(8)-a(9) from P. Christopher Staecker, Feb 24 2015

STATUS

approved

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Last modified June 17 14:09 EDT 2019. Contains 324185 sequences. (Running on oeis4.)