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A330725 a(0) = 0; thereafter a(n) = a(n-1) + sigma(n) if sigma(n) > a(n-1), otherwise a(n) = a(n-1) - sigma(n), where sigma is the sum of divisors function A000203. 2
0, 1, 4, 0, 7, 1, 13, 5, 20, 7, 25, 13, 41, 27, 3, 27, 58, 40, 1, 21, 63, 31, 67, 43, 103, 72, 30, 70, 14, 44, 116, 84, 21, 69, 15, 63, 154, 116, 56, 0, 90, 48, 144, 100, 16, 94, 22, 70, 194, 137, 44, 116, 18, 72, 192, 120, 0, 80, 170, 110, 278, 216, 120, 16 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..20000

MAPLE

a:= proc(n) option remember; `if`(n=0, 0, ((s, t)-> s+

      `if`(s<t, t, -t))(a(n-1), numtheory[sigma](n)))

    end:

seq(a(n), n=0..80);

CROSSREFS

Cf. A000203, A008344, A008345, A008348, A076042, A111466, A126646, A327442, A331165.

Sequence in context: A157698 A342360 A251967 * A057641 A336029 A272876

Adjacent sequences:  A330722 A330723 A330724 * A330726 A330727 A330728

KEYWORD

nonn,look

AUTHOR

Alois P. Heinz, Jan 11 2020

STATUS

approved

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Last modified July 27 15:49 EDT 2021. Contains 346308 sequences. (Running on oeis4.)