|
| |
|
|
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
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
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 !! (n-1)
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
|
| |
|
|
