A257349 a(1) = 16, a(n) = sigma(a(n-1)).

16, 31, 32, 63, 104, 210, 576, 1651, 1792, 4088, 8880, 28272, 79360, 196416, 633984, 1827840, 7074432, 22032000, 86640840, 364989240, 1651141800, 7540142400, 33541980160, 90193969152, 334471118520, 1415960985600, 6118878991680, 29424972595200

Offset: 1

Author

N. J. A. Sloane, May 01 2015

Keywords

• nonn

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000203, A007497, A051572, A257348.

Programs

Mathematica

NestList[DivisorSigma[1,#]&,16,27] (* Ivan N. Ianakiev, May 02 2015 *)

PARI

lista(nn) = {print1(v = 16, ", "); for (n=1, nn, v = sigma(v); print1(v, ", "););} \\ Michel Marcus, May 02 2015

Python

from itertools import accumulate, repeat # requires Python 3.2 or higher
from sympy import divisor_sigma
A257349_list = list(accumulate(repeat(16,100), lambda x, _: divisor_sigma(x)))
# Chai Wah Wu, May 02 2015