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A191783 Numbers k such that the topological k-sphere has a unique differentiable structure up to diffeomorphism. 0
1, 2, 3, 5, 6, 12, 61 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Whether 4 is a term is an open question. - Andrey Zabolotskiy, Feb 02 2018

Except (possibly) for k=4, these are the numbers k such that A001676(k)=1. - Jeppe Stig Nielsen, May 22 2019

LINKS

Table of n, a(n) for n=1..7.

John W. Milnor, Differential Topology Forty-six Years Later, Notices Amer. Math. Soc. 58 (2011), 804-809.

CROSSREFS

Cf. A001676.

Sequence in context: A007435 A125877 A118787 * A098930 A075372 A064725

Adjacent sequences:  A191780 A191781 A191782 * A191784 A191785 A191786

KEYWORD

nonn,more,hard

AUTHOR

N. J. A. Sloane, Jun 25 2011

EXTENSIONS

Definition rewritten by Jeppe Stig Nielsen, May 22 2019

STATUS

approved

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Last modified December 4 12:27 EST 2021. Contains 349495 sequences. (Running on oeis4.)