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A220290 4-hyperperfect numbers: n = 4*(sigma(n)-n-1) + 1. 7
1950625, 1220640625 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

m*5^n is in the sequence if m is prime of the form 5^(n+1) - 4.

186264514898681640625 is also a term.

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: A069339 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

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Last modified October 17 14:25 EDT 2018. Contains 316281 sequences. (Running on oeis4.)