%I #39 Nov 25 2019 09:04:20

%S 301,16513,60110701,1977225901,2733834545701,232630479398401

%N 6-hyperperfect numbers: n = 6*(sigma(n) - n - 1) + 1.

%C a(7) > 10^17. - _Max Alekseyev_, Nov 25 2019

%C (7^k-6)*7^(k-1) is a term for all k in A191469. - _Max Alekseyev_, Nov 17 2019

%C 336823287227717101 = 7^6*1340243*2136143 is also a term. - _Giovanni Resta_, Nov 18 2019

%H Antal Bege, Kinga Fogarasi, <a href="http://www.acta.sapientia.ro/acta-math/C1-1/MATH1-6.PDF">Generalized perfect numbers</a>, Acta Univ. Sapientiae, Math., 1 (2009), 73-82.

%H Judson S. McCranie, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL3/mccranie.html">A Study of Hyperperfect Numbers</a>, Journal of Integer Sequences, Vol. 3 (2000), Article 00.1.3.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HyperperfectNumber.html">Hyperperfect Number</a>

%o (PARI) isok(n) = 6*(sigma(n) - n - 1) + 1 == n; \\ _Michel Marcus_, Nov 18 2019

%Y Cf. A000396, A007593, A028500, A028501, A028502, A034916, A220290.

%K hard,more,nonn

%O 1,1

%A _Jud McCranie_

%E a(5) from _Donovan Johnson_, Nov 20 2012

%E a(6) from _Donovan Johnson_ confirmed by _Max Alekseyev_, Nov 17 2019