A116012 Numbers k such that k + sigma(k) + sigma(sigma(k)) is a fourth power.

19, 1873, 147497, 792736, 4551733, 4967176, 7333813, 8539521, 8674128, 12388853, 12948373, 18331664, 24834369, 36294936, 50952310, 116340016, 170434387, 196966352, 222505713, 236504256, 286766145, 390771936, 426323088, 532998481, 778930925, 805653001

Offset: 1

Author

Giovanni Resta, Feb 13 2006

Keywords

• nonn

Examples

			792736 + sigma(792736) + sigma(sigma(792736)) = 56^4.
		

Crossrefs

Cf. A116013, A116014, A116015.

Programs

PARI

for(n=1, 10^9, s=sigma(n); if(ispower(n+s+sigma(s), 4), print(n))) /* Donovan Johnson, Feb 17 2013 */

Extensions

a(5)-a(26) from Donovan Johnson, Feb 17 2013