A053868 Numbers whose sum of proper divisors is odd.

2, 3, 4, 5, 7, 8, 11, 13, 15, 16, 17, 18, 19, 21, 23, 27, 29, 31, 32, 33, 35, 36, 37, 39, 41, 43, 45, 47, 50, 51, 53, 55, 57, 59, 61, 63, 64, 65, 67, 69, 71, 72, 73, 75, 77, 79, 83, 85, 87, 89, 91, 93, 95, 97, 98, 99, 100, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119

Offset: 1

Author

Henry Bottomley, Mar 29 2000

Keywords

• nonn

Comments

Numbers which are twice squares, even squares or odd nonsquares.

Links

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

Crossrefs

Cf. A000203, A001065, A028982, A053869.

Programs

Haskell

a053868 n = a053868_list !! (n-1)
a053868_list = filter (odd . a001065) [1..]
-- Reinhard Zumkeller, Nov 01 2015, Sep 15 2011

Extensions

Improved name from Omar E. Pol, Aug 14 2009