A211657 - OEIS

A211657

Sigma(k) of numbers k such that value of sigma(k) is unique; sigma(k) = A000203(k) = sum of divisors of k.

1, 3, 4, 7, 6, 8, 15, 13, 28, 14, 39, 20, 36, 40, 30, 63, 91, 38, 44, 78, 57, 93, 62, 127, 68, 195, 74, 121, 112, 171, 217, 102, 162, 110, 133, 255, 176, 160, 204, 138, 222, 266, 150, 300, 158, 363, 164, 183, 260, 174, 508, 194, 198, 200, 465, 306, 212, 256, 330

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OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = sigma(A211656(n)).

EXAMPLE

For n = 4, a(n) = 7 because A211656(4) = 4; sigma (4) = 7.

CROSSREFS

Cf. A000203, A066076, A211656, A211658, A211659, A211660, A206036.

Cf. A007370 (sorted version of this sequence).