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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 (list; graph; refs; listen; history; text; internal format)
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*k-1) for k = 2 and 4,..,8. Better bounds are given in A242032.
LINKS
John Milnor, Differentiable Structures on Spheres, American Journal of Mathematics, Vol. 81, No. 4 (Oct., 1959), pp. 962-972. [See p. 971]
FORMULA
a(n) = A006530(A246053(n)). - Michel Marcus, Aug 18 2014
PROG
(Sage)
h = lambda x: zeta(2*x)*(4^x-2)
A246053 = lambda n: Integer((h((n+1)//2)*h(n//2)/h(n)).denominator())
A240978 = lambda n: max(prime_divisors(A246053(n)))
[A240978(n) for n in range(25)]
CROSSREFS
Sequence in context: A359582 A047003 A067352 * A242032 A350019 A298440
KEYWORD
nonn
AUTHOR
Peter Luschny, Aug 12 2014
STATUS
approved

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Last modified May 24 05:24 EDT 2024. Contains 372772 sequences. (Running on oeis4.)