OFFSET
1,1
LINKS
N. J. A. Sloane, Table of n, a(n) for n = 1..523
G. L. Cohen and H. J. J. te Riele, Iterating the sum-of-divisors function, Experimental Mathematics, 5 (1996), pp. 91-100.
Graeme L. Cohen and Herman J. J. te Riele, Iterating the Sum-of-Divisors Function, Experimental Mathematics, Vol. 5 (1996), No. 2, pp. 91-100.
MATHEMATICA
NestList[Plus@@Divisors[#] &, 5, 25] (* Alonso del Arte, Apr 28 2011 *)
PROG
(PARI) a=[5]; for(i=2, 10, a=concat(a, sigma(a[#a]))); a \\ Charles R Greathouse IV, Oct 03 2011
(Python)
from itertools import accumulate, repeat # requires Python 3.2 or higher
from sympy import divisor_sigma
A051572_list = list(accumulate(repeat(5, 100), lambda x, _: divisor_sigma(x)))
# Chai Wah Wu, May 02 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
STATUS
approved