A220290 4-hyperperfect numbers: n = 4*(sigma(n)-n-1) + 1.

1950625, 1220640625

Offset

1,1

Comments

For all k in A059613, (5^k-4)*5^(k-1) is a term. In particular, k=15 gives a term 186264514898681640625.

a(3) > 10^17. - Max Alekseyev, Nov 25 2019

Links

Table of n, a(n) for n=1..2.

Judson S. McCranie, A Study of Hyperperfect Numbers, Journal of Integer Sequences, Vol. 3 (2000), Article 00.1.3.

Eric Weisstein's World of Mathematics, Hyperperfect Number

Mathematica

Select[Range[1, 2*10^6, 4], # + 3 == 4*(DivisorSigma[1, #] - #) &]

Crossrefs

Cf. A000396, A007593, A028499-A028502, A034916.

Sequence in context: A350539 A109147 A251299 * A186578 A186579 A290500

Adjacent sequences: A220287 A220288 A220289 * A220291 A220292 A220293

Keyword

bref,hard,more,nonn

Author

Arkadiusz Wesolowski, Dec 11 2012

Status

approved