A228722 Largest number <= n with alternating parities of digits in decimal representation.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 12, 12, 14, 14, 16, 16, 18, 18, 18, 21, 21, 23, 23, 25, 25, 27, 27, 29, 30, 30, 32, 32, 34, 34, 36, 36, 38, 38, 38, 41, 41, 43, 43, 45, 45, 47, 47, 49, 50, 50, 52, 52, 54, 54, 56, 56, 58, 58, 58, 61, 61, 63, 63, 65, 65

Offset

0,3

Comments

a(n) <= n <= A228723(n) and A228710(a(n)) = 1;

a(A030141(n)) = A030141(n); a(A228709(n)) < A228709(n).

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Example

a(100) = 98; a(1000) = 989; a(10000) = 9898; a(100000) = 98989;
a(101) = 101; a(1001) = 989.

Prog

(Haskell)
a228722 n = head [x | x <- [n, n-1 ..], a228710 x == 1]

Crossrefs

Sequence in context: A122262 A172268 A017895 * A130024 A131232 A297238

Adjacent sequences: A228719 A228720 A228721 * A228723 A228724 A228725

Keyword

nonn,base

Author

Reinhard Zumkeller, Aug 31 2013

Status

approved