A202969 Number of arrays of 9 integers in -n..n with sum zero and adjacent elements differing in absolute value.

6, 5908, 229714, 3020170, 21274708, 102972822, 384996502, 1196677486, 3233011170, 7831389294, 17375280238, 35875950626, 69754837982, 128899962066, 228011800792, 388342150524, 639825818930, 1023746518060, 1595913984468

Offset: 1

Author

R. H. Hardin Dec 26 2011

Keywords

• nonn

Comments

Row 7 of A202962

Examples

			Some solutions for n=2
..1....1...-1...-1...-1....1...-1...-1...-1....0....0....2...-1...-1...-1....2
..0....0....0....2....0....2...-2....0...-2...-1...-2....1....0....2....0....1
..1...-1....2....0....2....0....0....2....1....0....1....2...-2...-1....1...-2
..2...-2....1....2....1...-1....2....0....2...-1....2...-1...-1....2....2...-1
.-1....0....2...-1...-2...-2....0...-1...-1....2...-1....0....0...-1....1....2
.-2...-1...-1...-2....1...-1...-2....2....0....0....0...-1....2....0...-2....0
..0....2....0...-1....0....2....0....1...-1....1....1....0....0....1....1....1
.-1...-1...-2....0...-1....1....2...-2....0....0...-2...-1....2...-2....0...-2
..0....2...-1....1....0...-2....1...-1....2...-1....1...-2....0....0...-2...-1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = a(n-1) -a(n-2) +2*a(n-3) +2*a(n-5) -a(n-7) -a(n-8) -5*a(n-9) -a(n-10) -5*a(n-11) +4*a(n-12) -a(n-13) +9*a(n-14) +4*a(n-15) +7*a(n-16) +2*a(n-17) -2*a(n-18) -4*a(n-19) -11*a(n-20) -5*a(n-21) -11*a(n-22) +2*a(n-23) -2*a(n-24) +11*a(n-25) +5*a(n-26) +11*a(n-27) +4*a(n-28) +2*a(n-29) -2*a(n-30) -7*a(n-31) -4*a(n-32) -9*a(n-33) +a(n-34) -4*a(n-35) +5*a(n-36) +a(n-37) +5*a(n-38) +a(n-39) +a(n-40) -2*a(n-42) -2*a(n-44) +a(n-45) -a(n-46) +a(n-47)