

A275996


Numbers n whose abundance is 64: sigma(n)  2n = 64.


3



108, 220, 6808, 8968, 14008, 24448, 66928, 552568, 786208, 1020568, 5303488, 8229568, 10001848, 133685248, 499722448, 2608895488, 4733164768, 7163795488, 13707973408, 14468025568, 16122444736
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OFFSET

1,1


COMMENTS

Any term x = a(m) of this sequence can be used with any term y of A275997 to satisfy the property (sigma(x)+sigma(y))/(x+y) = 2, which is a necessary (but not sufficient) condition for two numbers to be amicable.
The smallest amicable pair is (220, 284) = (a(2), A275997(2)) = (A063990(1), A063990(2)), where 284  220 = 64 is the abundance of 220 and the deficiency of 284.
The amicable pair (66928, 66992) = (a(7), A275997(11)) = (A063990(18), A063990(19)), and 66992  66928 = 64 is the abundance of 66928 and the deficiency of 66992.


LINKS

Table of n, a(n) for n=1..21.


EXAMPLE

a(1) = 108, since sigma(108)  2*108 = 280  216 = 64.


PROG

(PARI) isok(n) = sigma(n)  2*n == 64; \\ Michel Marcus, Dec 30 2016


CROSSREFS

Subsequence of A005101.
Cf. A002025, A063990, A275997, A088831, A088832, A088833, A141547, A175989, A275701, A066539, A259180.
Sequence in context: A044340 A044721 A095050 * A235292 A202202 A202195
Adjacent sequences: A275993 A275994 A275995 * A275997 A275998 A275999


KEYWORD

nonn


AUTHOR

Timothy L. Tiffin, Aug 16 2016


EXTENSIONS

a(14)a(15) from Michel Marcus, Dec 30 2016
a(16)a(21) from Lars Blomberg, Jan 12 2017


STATUS

approved



