cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-4 of 4 results.

A001676 Number of h-cobordism classes of smooth homotopy n-spheres.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 28, 2, 8, 6, 992, 1, 3, 2, 16256, 2, 16, 16, 523264, 24, 8, 4, 69524373504, 2, 4, 12, 67100672, 2, 3, 3, 7767211311104, 8, 32, 32, 3014494287036416, 6, 24, 120, 2303837503821447168, 192, 32, 96, 341653284209033216, 8, 11520, 48, 798366828940770681028608, 32, 12, 24, 11852230872517975212032, 24, 32, 8, 91678339751618435453288448, 1, 8, 4, 1986677733776616536315084668928, 4, 1, 24, 284423744326342962334231917756416
Offset: 1

Views

Author

Keywords

Comments

For n not equal to 4 (and possibly for all n) this is the number of oriented diffeomorphism classes of differentiable structures on the n-sphere.
a(3) = 1 follows now that the Poincaré conjecture has been proved.
a(n) for n != 4 is the order of S_n, the n-th group in Tables 1 and 2 (explained in Further Details p. 807) of Milnor 2011.
The sequence is essentially given in the rightmost column of tables 1 and 2 in Isaksen, Wang & Xu (2020). It corrects some errors in earlier work. - Andrey Zabolotskiy, Nov 27 2022

References

  • S. O. Kochman, Stable homotopy groups of spheres. A computer-assisted approach. Lecture Notes in Mathematics, 1423. Springer-Verlag, Berlin, 1990. 330 pp. ISBN: 3-540-52468-1. [Math. Rev. 91j:55016]
  • S. O. Kochman and M. E. Mahowald, On the computation of stable stems. The Cech Centennial (Boston, MA, 1993), 299-316, Contemp. Math., 181, Amer. Math. Soc., Providence, RI, 1995. [Math. Rev. 96j:55018]
  • 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.
  • J. W. Milnor and J. D. Stasheff, Characteristic Classes, Princeton, 1974, p. 285.
  • S. P. Novikov ed., Topology I, Encyc. of Math. Sci., vol. 12.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • H. Whitney, The work of John W. Milnor, pp. 48-50 of Proc. Internat. Congress Mathematicians, Stockholm, 1962.

Crossrefs

Extensions

More terms from Paul Muljadi, Mar 17 2011
Further terms from Jonathan Sondow, Jun 16 2011
The terms a(56), a(57), a(63) corrected by Andrey Zabolotskiy, Nov 27 2022

A228689 a(n) = A001676(4*n + 3).

Original entry on oeis.org

1, 28, 992, 16256, 523264, 69524373504, 67100672, 7767211311104, 3014494287036416, 2303837503821447168, 341653284209033216, 798366828940770681028608, 11852230872517975212032, 91678339751618435453288448, 1986677733776616536315084668928, 284423744326342962334231917756416
Offset: 0

Views

Author

N. J. A. Sloane, Aug 30 2013

Keywords

Crossrefs

Extensions

Term a(15) corrected by Andrey Zabolotskiy, Nov 27 2022

A228691 a(n) = A001676(4*n + 1).

Original entry on oeis.org

1, 1, 8, 3, 16, 8, 4, 3, 32, 24, 32, 11520, 12, 32, 8, 1, 6144, 32, 128, 256, 9216
Offset: 0

Views

Author

N. J. A. Sloane, Aug 30 2013

Keywords

Crossrefs

Extensions

Term a(14) corrected, a(16)-a(20) added by Andrey Zabolotskiy, Nov 27 2022

A228692 a(n) = A001676(4n+2).

Original entry on oeis.org

1, 1, 6, 2, 16, 4, 12, 3, 32, 120, 96, 48, 24, 8, 4, 24, 512, 512, 384, 384, 10752
Offset: 0

Views

Author

N. J. A. Sloane, Aug 30 2013

Keywords

Crossrefs

Extensions

More terms from the b-file at A001676 added by Amiram Eldar, May 03 2024
Showing 1-4 of 4 results.