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.
%I A240978 #29 Aug 19 2014 01:07:44 %S A240978 2,2,7,31,127,73,691,8191,3617,131071,524287,593,2294797,657931, %T A240978 362903,1001259881,2147483647,151628697551,26315271553053477373, %U A240978 154210205991661,1897170067619,1520097643918070802691,1798482437,67568238839737,153289748932447906241 %N A240978 The largest prime divisor of A246053(n). %C A240978 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. %H A240978 John Milnor, <a href="http://www.jstor.org/stable/2372998">Differentiable Structures on Spheres</a>, American Journal of Mathematics, Vol. 81, No. 4 (Oct., 1959), pp. 962-972. [See p. 971] %F A240978 a(n) = A006530(A246053(n)). - _Michel Marcus_, Aug 18 2014 %o A240978 (Sage) %o A240978 h = lambda x: zeta(2*x)*(4^x-2) %o A240978 A246053 = lambda n: Integer((h((n+1)//2)*h(n//2)/h(n)).denominator()) %o A240978 A240978 = lambda n: max(prime_divisors(A246053(n))) %o A240978 [A240978(n) for n in range(25)] %Y A240978 Cf. A246053, A246052, A242032. %K A240978 nonn %O A240978 0,1 %A A240978 _Peter Luschny_, Aug 12 2014