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 A163105 #19 Oct 07 2024 15:27:21
%S A163105 1,2,2,3,2,2,2,2,3,2,2,6,2,2,2,4,2,6,2,6,2,2,2,4,3,2,2,6,2,4,2,6,2,2,
%T A163105 2,2,2,2,2,4,2,4,2,6,6,2,2,6,3,6,2,6,2,4,2,4,2,2,2,6,2,2,6,4,2,4,2,6,
%U A163105 2,4,2,6,2,2,6,6,2,4,2,6,4,2,2,6,2,2,2,4,2,6,2,6,2,2,2,6,2,6,6,2,2,4,2,4,4
%N A163105 a(n) = tau(sigma(tau(n))), where tau = number of divisors of n (A000005), and sigma = sum of divisors of n (A000203).
%C A163105 Repeated application of tau (number of divisors) and sigma (sum of divisors).
%H A163105 Antti Karttunen, <a href="/A163105/b163105.txt">Table of n, a(n) for n = 1..10000</a>
%H A163105 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>
%F A163105 a(n) = A000005(A000203(A000005(n))) = A000005(A062069(n)) = A062068(A000005(n)).
%p A163105 with(numtheory) : A163105 := proc(n) tau(sigma(tau(n))) ; end: seq(A163105(n),n=1..120) ; # _R. J. Mathar_, Jul 27 2009
%t A163105 With[{s = DivisorSigma}, s[0, s[1, s[0, Range[100]]]]] (* _Paolo Xausa_, Oct 07 2024 *)
%o A163105 (PARI) A163105(n) = numdiv(sigma(numdiv(n))); \\ _Antti Karttunen_, Jul 23 2017
%Y A163105 Cf. A000005, A000203, A062068, A062069, A163106.
%K A163105 nonn
%O A163105 1,2
%A A163105 _Jaroslav Krizek_, Jul 20 2009
%E A163105 More terms from _R. J. Mathar_, Jul 27 2009
%E A163105 Name edited by _Antti Karttunen_, Jul 23 2017