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 A213698 Half the number of 3 X 3 0..n symmetric arrays with no 2 X 2 subblock summing to 2n. 1
 13, 192, 1320, 5470, 17499, 45892, 105856, 219564, 421825, 758560, 1296408, 2117882, 3336655, 5087460, 7549184, 10927192, 15486741, 21525024, 29417800, 39578070, 52519203, 68796772, 89091840, 114132100, 144799369, 182025792 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Row 2 of A213697. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA 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). 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 EXAMPLE Some solutions for n=4: ..0..3..4....2..0..1....0..1..1....4..4..4....3..0..0....2..4..3....3..1..1 ..3..0..3....0..2..0....1..3..2....4..1..2....0..1..4....4..3..2....1..2..0 ..4..3..3....1..0..0....1..2..4....4..2..4....0..4..2....3..2..2....1..0..2 CROSSREFS Cf. A213697. Sequence in context: A103731 A331495 A000563 * A159196 A177508 A228659 Adjacent sequences:  A213695 A213696 A213697 * A213699 A213700 A213701 KEYWORD nonn AUTHOR R. H. Hardin, Jun 18 2012 STATUS approved

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Last modified February 24 22:04 EST 2020. Contains 332216 sequences. (Running on oeis4.)