A249285 Number of length n+3 0..3 arrays with no four consecutive terms having the sum of any three elements equal to three times the fourth.
204, 660, 2144, 6960, 22572, 73204, 237480, 770416, 2499164, 8107012, 26298608, 85311248, 276744204, 897739412, 2912207432, 9447011744, 30645489228, 99411957620, 322485877472, 1046123080816, 3393554802188, 11008469603188
Offset: 1
Keywords
Examples
Some solutions for n=6: 3 0 3 2 1 1 3 0 0 0 3 3 1 2 0 2 3 1 3 2 0 1 1 0 1 2 1 3 0 3 2 2 1 1 2 1 3 1 3 2 0 2 0 1 1 2 2 1 2 1 3 1 3 0 1 0 2 0 1 1 1 2 0 0 0 0 2 3 1 0 3 2 3 3 3 2 3 0 2 0 2 3 0 3 1 1 0 2 0 1 1 2 0 0 0 1 2 3 1 3 3 0 3 0 1 3 0 0 2 2 2 1 3 0 3 1 3 1 3 3 1 1 2 1 0 3 1 3 3 1 1 1 2 0 3 2 0 2 0 0 0 2 2 0
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Column 3 of A249290.
Formula
Empirical: a(n) = 2*a(n-1) + 2*a(n-2) + 4*a(n-3) + 8*a(n-4) + 4*a(n-5) - 8*a(n-6) - 2*a(n-7) + 3*a(n-8).
Empirical g.f.: 4*x*(51 + 63*x + 104*x^2 + 134*x^3 + 23*x^4 - 133*x^5 - 18*x^6 + 48*x^7) / (1 - 2*x - 2*x^2 - 4*x^3 - 8*x^4 - 4*x^5 + 8*x^6 + 2*x^7 - 3*x^8). - Colin Barker, Nov 09 2018