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

Author

Giovanni Resta, Feb 13 2006

Keywords

• nonn

Examples

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

Crossrefs

Cf. A001358.