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 A163107 #11 Nov 07 2017 18:31:54 %S A163107 1,2,2,2,3,4,3,3,2,4,4,4,3,4,4,2,4,3,4,4,4,3,4,6,2,4,4,4,4,6,4,4,4,4, %T A163107 4,3,3,6,4,6,4,6,4,6,4,6,4,4,3,3,6,4,4,5,6,5,4,6,6,5,3,6,4,2,6,4,4,6, %U A163107 6,4,6,4,3,4,4,6,6,5,4,4,2,6,6,6,6,6,5,6,6,6,4,5,4,4,5,6,4,4,6,3,4,5,4,5,4 %N A163107 a(n) = tau(tau(sigma(n))), where tau = A000005, the number of divisors, and sigma = A000203, the sum of divisors of n. %C A163107 Repeated application of tau (number of divisors) and sigma (sum of divisors). %H A163107 Antti Karttunen, <a href="/A163107/b163107.txt">Table of n, a(n) for n = 1..16384</a> %F A163107 a(n) = A000005(A000005(A000203(n))) = A000005(A062068(n)) = A010553(A000203(n)). %p A163107 with(numtheory) : A163107 := proc(n) tau(tau(sigma(n))) ; end: seq(A163107(n),n=1..120) ; # _R. J. Mathar_, Jul 27 2009 %t A163107 DivisorSigma[0,DivisorSigma[0,DivisorSigma[1,Range[110]]]] (* _Harvey P. Dale_, Nov 25 2016 *) %o A163107 (PARI) A163107(n) = numdiv(numdiv(sigma(n))); \\ _Antti Karttunen_, Nov 07 2017 %Y A163107 Cf. A000005, A000203, A010553, A062068. %K A163107 nonn %O A163107 1,2 %A A163107 _Jaroslav Krizek_, Jul 20 2009 %E A163107 More terms from _R. J. Mathar_, Jul 27 2009