A250554 Number of length n+2 0..1 arrays with the sum of second differences multiplied by some arrangement of +-1 equal to zero.
2, 8, 14, 32, 62, 128, 254, 512, 1022, 2048, 4094, 8192, 16382, 32768, 65534, 131072, 262142, 524288, 1048574, 2097152, 4194302, 8388608, 16777214, 33554432, 67108862, 134217728, 268435454, 536870912, 1073741822, 2147483648, 4294967294
Offset: 1
Keywords
Examples
Some solutions for n=6: ..1....1....0....0....0....0....1....0....1....1....0....1....0....1....0....0 ..0....1....1....1....0....0....1....1....0....0....1....1....0....1....1....0 ..0....1....1....0....1....1....0....1....1....0....1....1....1....0....0....1 ..1....1....0....0....0....0....1....1....0....0....0....1....1....0....0....0 ..1....0....1....0....0....1....1....1....0....1....0....0....1....0....1....1 ..1....1....0....1....1....0....1....1....1....1....0....0....1....1....0....1 ..0....1....0....0....1....0....0....1....0....1....0....0....0....0....0....1 ..1....1....1....1....1....0....0....0....1....0....1....0....0....0....1....1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Column 1 of A250561.
Formula
Empirical: a(n) = 2*a(n-1) +a(n-2) -2*a(n-3).
Empirical: a(n) = 2^(n+1) for even n, 2^(n+1)-2 for odd n.
Empirical g.f.: 2*x*(1 + 2*x - 2*x^2) / ((1 - x)*(1 + x)*(1 - 2*x)). - Colin Barker, Nov 14 2018
Comments