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A317832 Denominators of rational valued sequence f whose Dirichlet convolution with itself yields A000203 (sigma, the sum of divisors). 5
1, 2, 1, 8, 1, 1, 1, 16, 2, 2, 1, 4, 1, 1, 1, 128, 1, 4, 1, 8, 1, 1, 1, 8, 1, 2, 1, 2, 1, 1, 1, 256, 1, 2, 1, 16, 1, 1, 1, 16, 1, 1, 1, 4, 2, 1, 1, 64, 2, 2, 1, 8, 1, 2, 1, 4, 1, 2, 1, 4, 1, 1, 1, 1024, 1, 1, 1, 8, 1, 1, 1, 32, 1, 2, 1, 4, 1, 1, 1, 128, 8, 2, 1, 1, 1, 1, 1, 8, 1, 4, 1, 2, 1, 1, 1, 128, 1, 4, 1, 8, 1, 1, 1, 16, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

Index entries for sequences related to sigma(n)

FORMULA

a(n) = denominator of f(n), where f(1) = 1, f(n) = (1/2) * (A000203(n) - Sum_{d|n, d>1, d<n} f(d) * f(n/d)) for n > 1.

PROG

(PARI)

A317831perA317832(n) = if(1==n, n, (sigma(n)-sumdiv(n, d, if((d>1)&&(d<n), A317831perA317832(d)*A317831perA317832(n/d), 0)))/2);

A317832(n) = denominator(A317831perA317832(n));

CROSSREFS

Cf. A317831 (gives the numerators).

Cf. also A000203, A299152.

Sequence in context: A021825 A323690 A152901 * A317928 A011327 A318454

Adjacent sequences:  A317829 A317830 A317831 * A317833 A317834 A317835

KEYWORD

nonn,frac

AUTHOR

Antti Karttunen, Aug 10 2018

STATUS

approved

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Last modified April 23 06:08 EDT 2019. Contains 322381 sequences. (Running on oeis4.)