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A066242 The floor((Log x)^2)-perfect numbers, where f-perfect numbers for an arithmetical function f are defined in A066218. 0
2, 18, 20, 32, 45, 63 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..6.

J. Pe, On a Generalization of Perfect Numbers, J. Rec. Math., 31(3) (2002-2003), 168-172.

EXAMPLE

Let f(n) = floor((Log x)^2). Then f(18) = 8 = 4+3+1+0+0 = f(9)+f(6)+f(3)f(2)+f(1); so 18 is a term of the sequence.

MATHEMATICA

f[x_ ] := Floor[Log[x]^2]; Select[ Range[2, 10^5], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ]

CROSSREFS

Sequence in context: A076378 A231502 A231864 * A022371 A299380 A266956

Adjacent sequences:  A066239 A066240 A066241 * A066243 A066244 A066245

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Dec 19 2001

STATUS

approved

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Last modified October 17 01:24 EDT 2018. Contains 316275 sequences. (Running on oeis4.)