A116035 Numbers k such that k + phi(k) + sigma(k) is a prime.

1, 4, 15, 33, 35, 36, 50, 55, 57, 64, 65, 75, 77, 85, 87, 93, 98, 115, 119, 129, 133, 143, 155, 159, 185, 187, 189, 205, 213, 215, 217, 219, 242, 243, 247, 253, 265, 287, 295, 303, 309, 323, 324, 327, 339, 345, 365, 385, 393, 395, 407, 425, 427, 453, 469, 493

Offset: 1

Author

Giovanni Resta, Feb 13 2006

Keywords

• nonn

Examples

			205 + phi(205) + sigma(205) = 617 (prime).
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A078762, A068080.

Programs

Mathematica

Select[Range[500],PrimeQ[#+EulerPhi[#]+DivisorSigma[1,#]]&] (* Harvey P. Dale, Nov 09 2014 *)