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

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).

Sequence in context: A295565 A086455 A204823 * A215430 A096842 A147966

Adjacent sequences: A211654 A211655 A211656 * A211658 A211659 A211660

Keyword

nonn

Author

Jaroslav Krizek, Apr 20 2012

Status

approved