

A240978


The largest prime divisor of A246053(n).


4



2, 2, 7, 31, 127, 73, 691, 8191, 3617, 131071, 524287, 593, 2294797, 657931, 362903, 1001259881, 2147483647, 151628697551, 26315271553053477373, 154210205991661, 1897170067619, 1520097643918070802691, 1798482437, 67568238839737, 153289748932447906241
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OFFSET

0,1


COMMENTS

According to theorem 2 of the Milnor paper a(2) and a(4) through a(8) are lower bounds for the number of distinct differentiable structures on spheres S^(4*k1) for k = 2 and 4,..,8. Better bounds are given in A242032.


LINKS



FORMULA



PROG

(Sage)
h = lambda x: zeta(2*x)*(4^x2)
A246053 = lambda n: Integer((h((n+1)//2)*h(n//2)/h(n)).denominator())


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



