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A109321 Admirable numbers n such that the subtracted divisor is > sqrt(n). 1
24, 30, 84, 120, 140, 224, 234, 270, 308, 364, 476, 532, 644, 672, 1488, 1638, 2480, 3472, 3724, 4095, 5456, 5624, 6200, 6435, 6448, 8432, 9424, 11408, 14384, 15872, 18352, 20336, 21328, 23312, 24384, 26288, 29264, 29450, 30256, 33232, 35150 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Solutions to sigma(x)=2(x+d) with d > sqrt(x) being a proper divisor of x. The subsequence A165772 contains most of the terms. - M. F. Hasler, Oct 11 2009

LINKS

Table of n, a(n) for n=1..41.

EXAMPLE

a(2)=30 because 1+2+3+5+10+15-6 = 30 and 6 > sqrt(30) = 5.477...

PROG

(PARI) is_A109321(n)= my(d=sigma(n)-2*n); d>0 && bittest(d, 0)==0 && d<2*n && d*d>4*n && 2*n%d==0 \\ M. F. Hasler, Oct 11 2009

CROSSREFS

Cf. A111592.

Sequence in context: A228875 A175258 A135045 * A067952 A239801 A123200

Adjacent sequences:  A109318 A109319 A109320 * A109322 A109323 A109324

KEYWORD

nonn

AUTHOR

Jason Earls, Aug 20 2005

STATUS

approved

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Last modified March 19 15:02 EDT 2019. Contains 321330 sequences. (Running on oeis4.)