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A166069 Multiply perfect numbers k such that sigma(k)/k > 2. 6
120, 672, 30240, 32760, 523776, 2178540, 23569920, 45532800, 142990848, 459818240, 1379454720, 1476304896, 14182439040, 31998395520, 43861478400, 51001180160, 66433720320, 153003540480, 403031236608, 518666803200 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of multiply perfect numbers (A007691). Numbers k = A007691(n) such that sigma(A007691(n))/A007691(n) > 2. Numbers k = A007691(n) such that A054030(n) > 2.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n=1..1587

Achim Flammenkamp, The Multiply Perfect Numbers Page

EXAMPLE

For n = 1 the a(1) = 120, sigma(120) / 120 = 360 / 120 = 3, i.e. > 2.

MAPLE

with(numtheory); P:=proc(q) local a, n;

for n from 1 to q do a:=sigma(n)/n; if type(a, integer) and a>2 then print(n);

fi; od; end: P(10^6); # Paolo P. Lava, Oct 24 2013

PROG

(PARI) isok(n) = sn = sigma(n)/n ; (type(sn) == "t_INT") && (sn > 2); \\ Michel Marcus, Oct 24 2013

CROSSREFS

Sequence in context: A306373 A113546 A281771 * A114887 A069085 A039688

Adjacent sequences:  A166066 A166067 A166068 * A166070 A166071 A166072

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Oct 06 2009

EXTENSIONS

Extended by Charles R Greathouse IV, Oct 12 2009

STATUS

approved

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Last modified February 20 04:34 EST 2020. Contains 332063 sequences. (Running on oeis4.)