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