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 A257349 #13 May 02 2015 22:46:05
%S A257349 16,31,32,63,104,210,576,1651,1792,4088,8880,28272,79360,196416,
%T A257349 633984,1827840,7074432,22032000,86640840,364989240,1651141800,
%U A257349 7540142400,33541980160,90193969152,334471118520,1415960985600,6118878991680,29424972595200
%N A257349 a(1) = 16, a(n) = sigma(a(n-1)).
%H A257349 Chai Wah Wu, <a href="/A257349/b257349.txt">Table of n, a(n) for n = 1..1000</a>
%t A257349 NestList[DivisorSigma[1,#]&,16,27] (* _Ivan N. Ianakiev_, May 02 2015 *)
%o A257349 (Python)
%o A257349 from itertools import accumulate, repeat # requires Python 3.2 or higher
%o A257349 from sympy import divisor_sigma
%o A257349 A257349_list = list(accumulate(repeat(16,100), lambda x, _: divisor_sigma(x)))
%o A257349 # _Chai Wah Wu_, May 02 2015
%o A257349 (PARI) lista(nn) = {print1(v = 16, ", "); for (n=1, nn, v = sigma(v); print1(v, ", "););} \\ _Michel Marcus_, May 02 2015
%Y A257349 Cf. A000203, A007497, A051572, A257348.
%K A257349 nonn
%O A257349 1,1
%A A257349 _N. J. A. Sloane_, May 01 2015