A213802 Number of 4X4 0..n symmetric arrays with all rows summing to 2*n.
18, 169, 880, 3249, 9522, 23753, 52544, 106009, 198770, 351233, 590832, 953625, 1485778, 2245489, 3304704, 4751377, 6691410, 9251257, 12580080, 16852705, 22271986, 29072121, 37521216, 47924969, 60629426, 76025041, 94549616
Offset: 1
Keywords
Examples
Some solutions for n=4 ..2..3..2..1....3..1..1..3....0..1..3..4....2..4..0..2....1..3..1..3 ..3..2..0..3....1..4..1..2....1..0..4..3....4..2..2..0....3..4..0..1 ..2..0..3..3....1..1..3..3....3..4..1..0....0..2..3..3....1..0..3..4 ..1..3..3..1....3..2..3..0....4..3..0..1....2..0..3..3....3..1..4..0
Links
- R. H. Hardin, Table of n, a(n) for n = 1..173
Formula
Empirical: a(n) = 4*a(n-1) -3*a(n-2) -8*a(n-3) +14*a(n-4) -14*a(n-6) +8*a(n-7) +3*a(n-8) -4*a(n-9) +a(n-10).
Empirical: G.f. -x*(18+97*x+258*x^2+380*x^3+266*x^4+86*x^5+22*x^6+4*x^7-4*x^8+x^9) / ( (1+x)^3*(x-1)^7 ). - R. J. Mathar, Jul 04 2012
Comments