The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.


(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A191783 Numbers k such that the topological k-sphere has a unique differentiable structure up to diffeomorphism. 2
1, 2, 3, 5, 6, 12, 56, 61 (list; graph; refs; listen; history; text; internal format)
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
The list in Milnor's paper (p. 807, A358290) does not include the term 56 because it was only discovered later that it is actually a term of this list, see Wang & Xu, Theorem 1.14. - Andrey Zabolotskiy, Nov 29 2022
Dimensions without exotic spheres. - Charles R Greathouse IV, Dec 22 2022
Brady Haran and Ciprian Manolescu, The Puzzling Fourth Dimension (and exotic shapes), Numberphile video (2022).
John W. Milnor, Differential Topology Forty-six Years Later, Notices Amer. Math. Soc. 58 (2011), 804-809.
Guozhen Wang and Zhouli Xu, The triviality of the 61-stem in the stable homotopy groups of spheres, Annals of Mathematics, 186 (2017), 501-580; arXiv:1601.02184 [math.AT], 2016-2017.
Sequence in context: A125877 A118787 A359668 * A358290 A098930 A075372
N. J. A. Sloane, Jun 25 2011
Definition rewritten by Jeppe Stig Nielsen, May 22 2019
The term a(7) = 56 inserted by Andrey Zabolotskiy, Nov 27 2022

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 16 14:12 EDT 2024. Contains 373430 sequences. (Running on oeis4.)