A239726 - OEIS

A239726

Numbers n such that sigma(n) - n = sigma(n') - n', where n' is the arithmetic derivative of n.

1, 4, 27, 369, 2120, 2853, 3125, 6620, 24932, 65588, 210404, 245444, 347049, 823543, 833444, 968204, 1610684, 3125492, 5046044, 5856308, 9339020, 9900236, 10614092, 10636772, 11421164, 11617772, 13276892, 16116764, 16244156, 18422444, 21073916, 21656564

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OFFSET

1,2

COMMENTS

A051674 is a subset of this sequence.

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

Arithmetic derivative of 369 is 255, sigma(369) = 546, sigma(255) = 432 and 546 - 369 = 432 - 255 = 177.

MAPLE

with(numtheory); P:=proc(q) local a, n, p;

for n from 1 to q do a:=n*add(op(2, p)/op(1, p), p=ifactors(n)[2]);