A057617 - OEIS

A057617

Order of subgroup bP_{m+1} of group Theta_m of h-cobordism classes of smooth homotopy m-spheres defined by those homotopy m-spheres which bound parallelizable (m+1)-manifolds, where m = 2n+1.

1, 1, 1, 28, 2, 992, 1, 8128, 2, 130816

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OFFSET

0,4

COMMENTS

a(1) = 1 because the Poincaré conjecture is true.

REFERENCES

M. A. Kervaire and J. W. Milnor, Groups of homotopy spheres: I. Ann. of Math. (2) 77 1963 504-537.

J. P. Levine, Lectures on groups of homotopy spheres. In Algebraic and geometric topology (New Brunswick, NJ, 1983), 62-95, Lecture Notes in Math., 1126, Springer, Berlin, 1985.

LINKS

Table of n, a(n) for n=0..9.

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

CROSSREFS

Cf. A001676.

Sequence in context: A358706 A040782 A040783 * A040771 A040770 A040772

Adjacent sequences: A057614 A057615 A057616 * A057618 A057619 A057620

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 03 2002

EXTENSIONS

a(0)-a(1) from Andrey Zabolotskiy, Feb 02 2018

STATUS

approved