A248465 Number of length 4+2 0..n arrays with no three consecutive terms having the sum of any two elements equal to twice the third.
26, 144, 1436, 6040, 21182, 56782, 138534, 295078, 589916, 1082878, 1900666, 3161064, 5083368, 7857546, 11844802, 17344202, 24892396, 34927864, 48224830, 65403924, 87536430, 115449764, 150581308, 194049230, 247712034, 312987618
Offset: 1
Keywords
Examples
Some solutions for n=6 ..2....0....4....4....3....3....1....2....3....1....4....4....2....3....1....5 ..6....4....0....1....5....2....6....2....1....0....6....1....3....3....4....6 ..2....6....3....1....5....3....0....1....0....6....1....1....2....4....3....0 ..5....6....2....3....6....5....1....6....1....4....5....6....5....1....6....4 ..6....3....6....1....1....0....1....0....4....1....0....3....1....5....6....3 ..6....6....3....4....2....1....4....2....0....1....4....5....2....2....2....6
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-5) +3*a(n-6) +4*a(n-7) +3*a(n-8) +2*a(n-9) -3*a(n-11) -4*a(n-12) -6*a(n-13) -5*a(n-14) -5*a(n-15) +3*a(n-18) +2*a(n-19) +4*a(n-20) +a(n-21) -a(n-23) +2*a(n-25) +2*a(n-26) +5*a(n-27) +3*a(n-28) +5*a(n-29) -5*a(n-32) -3*a(n-33) -5*a(n-34) -2*a(n-35) -2*a(n-36) +a(n-38) -a(n-40) -4*a(n-41) -2*a(n-42) -3*a(n-43) +5*a(n-46) +5*a(n-47) +6*a(n-48) +4*a(n-49) +3*a(n-50) -2*a(n-52) -3*a(n-53) -4*a(n-54) -3*a(n-55) -2*a(n-56) +a(n-59) +a(n-60) +a(n-61)
Comments