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

1,2

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

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

Prog

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

Crossrefs

Cf. A000396 (perfect numbers).

Sequence in context: A047253 A248910 A254278 * A037918 A043091 A031943

Adjacent sequences: A204875 A204876 A204877 * A204879 A204880 A204881

Keyword

nonn

Author

Reinhard Zumkeller, Jan 20 2012

Status

approved