login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Number of zero-sum -1..1 arrays of n elements with first and second differences also in -1..1
1

%I #6 Mar 31 2012 12:36:45

%S 1,1,3,3,5,11,21,39,73,129,229,407,733,1335,2461,4549,8427,15585,

%T 28811,53235,98479,182403,338461,628873,1169875,2177875,4056997,

%U 7561019,14098931,26303445,49100159,91702815,171359391,320357055,599167829

%N Number of zero-sum -1..1 arrays of n elements with first and second differences also in -1..1

%C Column 1 of A201873

%H R. H. Hardin, <a href="/A201866/b201866.txt">Table of n, a(n) for n = 1..210</a>

%e Some solutions for n=10

%e ..1....1....1...-1...-1....0...-1....1....0...-1...-1....1....0....0...-1...-1

%e ..1....1....1....0....0....0....0....1...-1...-1...-1....1....1....0....0...-1

%e ..0....0....1....0....0....0....1....0...-1...-1...-1....1....1...-1....0....0

%e .-1....0....0...-1....0....0....1....0....0....0....0....1....0...-1....0....0

%e .-1....0....0...-1....1....0....1....0....0....0....0....0...-1...-1....0....1

%e .-1....0...-1....0....1...-1....0....0....0....0....1....0...-1....0....1....1

%e .-1....0...-1....1....0...-1....0...-1....0....1....1...-1...-1....0....1....1

%e ..0...-1...-1....1....0....0...-1...-1....0....1....0...-1....0....1....0....0

%e ..1...-1....0....1....0....1...-1....0....1....1....0...-1....0....1....0....0

%e ..1....0....0....0...-1....1....0....0....1....0....1...-1....1....1...-1...-1

%K nonn

%O 1,3

%A _R. H. Hardin_ Dec 06 2011