A109728 - OEIS

%I #2 Mar 31 2012 13:46:52

%S 1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,12,12,14,14,16,16,18,18,20,

%T 21,21,23,23,25,25,27,27,29,29,31,32,32,34,34,36,36,38,38,40,41,41,43,

%U 43,45,45,47,47,49,49,51,52,52,54,54,56,56,58,58,60,61,61,63,63

%N A self-describing sequence.

%F There are a(n) digits having the same parity as a(n) in the interval ]0;a(n)+1[.

%e Pick the first "4" in the sequence; "4" is even; there are 4 even digits in the interval ]0;5[ -> 2,2,4 and 4.

%e Take "21", which is odd; there are 21 odd digits in the interval ]0;22[ -> 1 3 3 5 5 7 7 9 9 1 1 1 1 1 1 1 1 1 1 1 and 1 = 21.

%K base,easy,nonn

%O 0,2

%A _Eric Angelini_, Aug 09 2005; revised Aug 25 2005