A202967 Number of arrays of 7 integers in -n..n with sum zero and adjacent elements differing in absolute value.

6, 524, 9872, 66208, 289536, 941086, 2537024, 5933492, 12515772, 24295760, 44188086, 76110890, 125357152, 198686606, 304811136, 454458544, 660981870, 940393644, 1312104510, 1798910920, 2427885688, 3230300850, 4242680088

Offset: 1

Author

R. H. Hardin Dec 26 2011

Keywords

• nonn

Comments

Row 5 of A202962

Examples

			Some solutions for n=4
..4....0....2...-4....3...-2...-2...-3....0...-1...-2....3....2....0....0...-4
.-2...-3....3....2....0....3...-4...-1...-1....3....3...-2....3....3....3....2
..4...-1....0...-4...-2...-1....1....0...-4....4...-4....1...-2...-1....4...-4
..0....2...-4....2....1...-3...-4....2....2....3....1....2....3...-2...-2....1
.-3....4...-2...-1...-4....0....2....1...-4...-2....0....0...-4....4...-4...-2
..1....0...-3....3...-1....4....4....2....3...-4....4...-4....0....0....2....4
.-4...-2....4....2....3...-1....3...-1....4...-3...-2....0...-2...-4...-3....3
		

Links

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

Formula

Empirical: a(n) = 2*a(n-1) -a(n-2) +a(n-3) -2*a(n-5) +a(n-6) -3*a(n-7) +3*a(n-8) -a(n-9) +2*a(n-10) +a(n-11) -a(n-13) -2*a(n-14) +a(n-15) -3*a(n-16) +3*a(n-17) -a(n-18) +2*a(n-19) -a(n-21) +a(n-22) -2*a(n-23) +a(n-24)