The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 10 08:09 EDT 2021. Contains 342845 sequences. (Running on oeis4.)