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A257349 a(1) = 16, a(n) = sigma(a(n-1)). 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MATHEMATICA

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

PROG

(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

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

CROSSREFS

Cf. A000203, A007497, A051572, A257348.

Sequence in context: A129617 A221257 A194122 * A167997 A185979 A185980

Adjacent sequences:  A257346 A257347 A257348 * A257350 A257351 A257352

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, May 01 2015

STATUS

approved

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Last modified July 23 11:44 EDT 2019. Contains 325254 sequences. (Running on oeis4.)