2,2

a(0) = 1 and presumably a(1) = 1 if the Poincare conjecture is true.

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.

Adjacent sequences: A057614 A057615 A057616 this_sequence A057618 A057619 A057620

Sequence in context: A001676 A040782 A040783 this_sequence A013533 A013546 A040771

nonn

njas, Feb 03 2002