cp's OEIS Frontend

A213698 Half the number of 3 X 3 0..n symmetric arrays with no 2 X 2 subblock summing to 2n.

%I A213698 #8 Jul 22 2018 06:42:10
%S A213698 13,192,1320,5470,17499,45892,105856,219564,421825,758560,1296408,
%T A213698 2117882,3336655,5087460,7549184,10927192,15486741,21525024,29417800,
%U A213698 39578070,52519203,68796772,89091840,114132100,144799369,182025792
%N A213698 Half the number of 3 X 3 0..n symmetric arrays with no 2 X 2 subblock summing to 2n.
%C A213698 Row 2 of A213697.
%H A213698 R. H. Hardin, <a href="/A213698/b213698.txt">Table of n, a(n) for n = 1..210</a>
%F A213698 Empirical: a(n) = 3*a(n-1) + a(n-2) - 11*a(n-3) + 6*a(n-4) + 14*a(n-5) - 14*a(n-6) - 6*a(n-7) + 11*a(n-8) - a(n-9) - 3*a(n-10) + a(n-11).
%F A213698 Empirical g.f.: x*(13 + 153*x + 731*x^2 + 1461*x^3 + 1803*x^4 + 1111*x^5 + 425*x^6 + 59*x^7 + 4*x^8) / ((1 - x)^7*(1 + x)^4). - _Colin Barker_, Jul 22 2018
%e A213698 Some solutions for n=4:
%e A213698 ..0..3..4....2..0..1....0..1..1....4..4..4....3..0..0....2..4..3....3..1..1
%e A213698 ..3..0..3....0..2..0....1..3..2....4..1..2....0..1..4....4..3..2....1..2..0
%e A213698 ..4..3..3....1..0..0....1..2..4....4..2..4....0..4..2....3..2..2....1..0..2
%Y A213698 Cf. A213697.
%K A213698 nonn
%O A213698 1,1
%A A213698 _R. H. Hardin_, Jun 18 2012