A116051 n+sigma(n)+sigma(sigma(n)) is a semiprime (A001358).

2, 3, 6, 11, 13, 17, 20, 33, 39, 45, 47, 52, 57, 58, 59, 61, 63, 64, 69, 81, 83, 85, 86, 89, 91, 98, 100, 103, 110, 115, 117, 123, 128, 133, 134, 135, 136, 141, 142, 143, 144, 145, 149, 150, 153, 154, 156, 158, 162, 164, 167, 173, 179, 181, 184, 185, 187, 189

Offset

1,1

Links

Table of n, a(n) for n=1..58.

Example

115 + sigma(115) + sigma(sigma(115)) = 662 = 2*331

Crossrefs

Cf. A001358.

Sequence in context: A152038 A105614 A116441 * A124593 A125882 A057758

Adjacent sequences: A116048 A116049 A116050 * A116052 A116053 A116054

Keyword

nonn

Author

Giovanni Resta, Feb 13 2006

Status

approved