A030340 - OEIS

%I #12 Jul 13 2013 12:01:54

%S 1,0,1,1,2,3,4,3,2,2,1,2,1,0,1,1,1,2,2,3,4,4,3,4,5,5,6,7,8,9,10,9,10,

%T 9,9,10,9,10,11,10,9,8,8,8,7,7,8,7,7,6,5,6,6,5,6,7,6,7,6,5,4,4,3,2,3,

%U 2,1,0,1,1,1,1,2,2,2,3,4,4,4,3,4,4,5,5

%N a(n)=(# 1's)-(# 2's) in first n terms of A003137.

%C This sequence is nonnegative: in any group of numbers with the same number of digits, the number with a 1 in a particular position always occurs before the number with a 2 in that position. In fact, 0's only occur on the last digits of (3^N)-1, where N is an integer, not the sequence index - Larry Reeves (larryr(AT)acm.org), Sep 25 2000

%H Reinhard Zumkeller, <a href="/A030340/b030340.txt">Table of n, a(n) for n = 1..10000</a>

%o (Haskell)

%o a030340 n = a030340_list !! (n-1)

%o a030340_list = scanl1

%o    (\u v -> u + fromEnum (v == 1) - fromEnum (v == 2)) a003137_list

%o -- _Reinhard Zumkeller_, Feb 21 2013

%Y Cf. A030339.

%K nonn,base

%O 1,5

%A _Clark Kimberling_

%E More terms from Larry Reeves (larryr(AT)acm.org), Sep 25 2000

%E Some data corrected by _Reinhard Zumkeller_, Feb 21 2013