OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 60*a(n-1) - 300*a(n-2) + 1500*a(n-3) - 7500*a(n-4) + 3125*a(n-5) for n>7.
Empirical g.f.: x*(32 - 51*x + 43870*x^2 - 951400*x^3 + 1096750*x^4 - 86739375*x^5 + 39912500*x^6) / ((1 - 5*x)*(1 - 55*x + 25*x^2 - 1375*x^3 + 625*x^4)). - Colin Barker, Jan 03 2019
EXAMPLE
Some solutions for n=3:
..9..1.11.12.13..5..6....0..1..2..3.20..5..6....9.10.18.19..4..5..6
..7.24..0.19.27..3..4...16..8.25.19.11.12.13....7.24..0.26.27.12.13
.23.15.16.26..2.10.20...23.15..7.26.18.10..4...23.15.25..1..2..3.20
.21.22.14..8.25.17.18...21.22.14.24..9.17.27...21.22.14..8.16.17.11
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 01 2015
STATUS
approved