A204878 Numbers that cannot be written as sum of perfect numbers.

1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 25, 26, 27, 29, 31, 32, 33, 35, 37, 38, 39, 41, 43, 44, 45, 47, 49, 50, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105

Offset: 1

Author

Reinhard Zumkeller, Jan 20 2012

Keywords

• nonn

Comments

Complement of A204879; A097796(a(n)) = 0.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
• Eric Weisstein's World of Mathematics, Perfect Number
• Wikipedia, Perfect number

Crossrefs

Cf. A000396 (perfect numbers).

Programs

Haskell

import Data.List (elemIndices)
a204878 n = a204878_list !! (n-1)
a204878_list = map (+ 1) $ elemIndices 0 a097796_list

Formula

a(38+k) = 49+2k for all k>0 (up to occurrence of an odd perfect number, known to be > 10^300, if it exists). - M. F. Hasler, Feb 09 2012