

A125640


Primitive doubly abundant numbers  doubly abundant numbers that are not the multiple of another doubly abundant number.


2



24, 30, 42, 54, 66, 78, 102, 114, 138, 140, 174, 176, 186, 222, 224, 246, 258, 282, 308, 318, 340, 354, 364, 366, 380, 402, 426, 438, 440, 474, 476, 498, 520, 532, 534, 580, 582, 606, 618, 642, 644, 654, 678, 762, 786, 812, 822, 834, 868, 894
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OFFSET

1,1


COMMENTS

Are there infinitely many primitive doubly abundant numbers?


LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000


EXAMPLE

42 is a primitive doubly abundant number because it is abundant (s(42) = 54), the sum of its proper divisors is abundant (s(54) = 66) and no divisor of 42 is doubly abundant.


PROG

(Haskell)
import Data.List (intersect)
a125640 n = a125640_list !! (n1)
a125640_list = f a125639_list [] where
f (x:xs) ys = if null (a027751_row' x `intersect` ys)
then x : f xs (x : ys) else f xs ys
 Reinhard Zumkeller, Oct 31 2015


CROSSREFS

Cf. A005101, A125639.
Cf. A027751.
Sequence in context: A335054 A125639 A076496 * A141545 A106682 A334790
Adjacent sequences: A125637 A125638 A125639 * A125641 A125642 A125643


KEYWORD

nonn


AUTHOR

Gabriel Cunningham (gabriel.cunningham(AT)gmail.com), Nov 28 2006


EXTENSIONS

Data corrected by Reinhard Zumkeller, Oct 31 2015


STATUS

approved



