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

1,1

Comments

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

Links

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

Prog

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

Crossrefs

Cf. A000203, A001065, A028982, A053869.

Sequence in context: A058586 A090467 A177202 * A241912 A269870 A307824

Adjacent sequences: A053865 A053866 A053867 * A053869 A053870 A053871

Keyword

nonn

Author

Henry Bottomley, Mar 29 2000

Extensions

Improved name from Omar E. Pol, Aug 14 2009

Status

approved