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 A163106 #11 Oct 14 2017 12:46:04 %S A163106 1,4,4,7,4,8,4,8,7,8,4,28,4,8,8,12,4,28,4,28,8,8,4,24,7,8,8,28,4,24,4, %T A163106 28,8,8,8,14,4,8,8,24,4,24,4,28,28,8,4,39,7,28,8,28,4,24,8,24,8,8,4, %U A163106 56,4,8,28,15,8,24,4,28,8,24,4,56,4,8,28,28,8,24,4,39,12,8,4,56,8,8,8,24,4 %N A163106 a(n) = sigma(sigma(tau(n))), where tau = number of divisors and sigma = sum of divisors. %C A163106 Repeated application of tau (number of divisors) and sigma (sum of divisors). %H A163106 Antti Karttunen, <a href="/A163106/b163106.txt">Table of n, a(n) for n = 1..10000</a> %F A163106 a(n) = A000203(A000203(A000005(n))) = A000203(A062069(n)) = A051027(A000005(n)). %p A163106 with(numtheory) : A163106 := proc(n) sigma(sigma(tau(n))) ; end: seq(A163106(n),n=1..120) ; # _R. J. Mathar_, Jul 27 2009 %t A163106 DivisorSigma[1,DivisorSigma[1,DivisorSigma[0,Range[90]]]] (* _Harvey P. Dale_, Oct 14 2017 *) %o A163106 (PARI) A163106(n) = sigma(sigma(numdiv(n))); \\ _Antti Karttunen_, May 25 2017 %Y A163106 Cf. A000005, A000203, A051027, A062069. %K A163106 nonn %O A163106 1,2 %A A163106 _Jaroslav Krizek_, Jul 20 2009 %E A163106 More terms from _R. J. Mathar_, Jul 27 2009