A200557 Number of -n..n arrays x(0..6) of 7 elements with zero sum and nonzero second differences.
142, 4978, 43698, 211374, 737460, 2076774, 5012084, 10807826, 21368704, 39388482, 68614738, 114064374, 182196622, 281328582, 421889370, 616590012, 881040966, 1234022180, 1697613488, 2298081194, 3066132222, 4036964078, 5251498784
Offset: 1
Keywords
Examples
Some solutions for n=3 .-3....2....0...-1...-1....0....0...-1...-1....2....3....1....1...-2...-3....1 ..0...-3...-1....0...-3....0...-2....1...-3....2...-2...-1....3....2....3....2 .-3....0....0...-3....1....1...-2...-2....3...-2...-2....1....0....0...-3...-1 ..3....0....2...-3....1...-3....3....0....0....0....0...-1....0...-3....2....3 ..3...-1....3....3....3....3....3...-1....3....1...-3...-1...-1....1....0...-2 .-2....2...-2....3...-1....2....1....1....0...-2....1....1...-3....2....3...-1 ..2....0...-2....1....0...-3...-3....2...-2...-1....3....0....0....0...-2...-2
Links
- R. H. Hardin, Table of n, a(n) for n = 1..146
Formula
Empirical: a(n) = 3*a(n-1) -6*a(n-2) +11*a(n-3) -16*a(n-4) +21*a(n-5) -24*a(n-6) +23*a(n-7) -19*a(n-8) +10*a(n-9) +a(n-10) -13*a(n-11) +25*a(n-12) -34*a(n-13) +40*a(n-14) -41*a(n-15) +37*a(n-16) -28*a(n-17) +14*a(n-18) +3*a(n-19) -20*a(n-20) +34*a(n-21) -42*a(n-22) +42*a(n-23) -34*a(n-24) +20*a(n-25) -3*a(n-26) -14*a(n-27) +28*a(n-28) -37*a(n-29) +41*a(n-30) -40*a(n-31) +34*a(n-32) -25*a(n-33) +13*a(n-34) -a(n-35) -10*a(n-36) +19*a(n-37) -23*a(n-38) +24*a(n-39) -21*a(n-40) +16*a(n-41) -11*a(n-42) +6*a(n-43) -3*a(n-44) +a(n-45)
Comments