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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A201270 Number of n X n 0..2 arrays with every row and column nondecreasing rightwards and downwards, and the number of instances of each value within one of each other.

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%I A201270 #16 Mar 18 2024 10:36:37
%S A201270 1,3,5,7,85,556,1260,27008,215577,613916,16442049,152673459,487975060,
%T A201270 14392411292,144918917509,496264541787,15559415313705,165127072154120,
%U A201270 592098075114238,19339952787547252,212870280758956694,788675446037414831,26535438036570486429,300014957716483809886
%N A201270 Number of n X n 0..2 arrays with every row and column nondecreasing rightwards and downwards, and the number of instances of each value within one of each other.
%e A201270 Some solutions for n=5
%e A201270 ..0..0..0..0..2....0..0..0..0..2....0..0..0..0..0....0..0..0..0..0
%e A201270 ..0..0..1..2..2....0..0..1..1..2....0..0..0..1..1....0..0..1..2..2
%e A201270 ..0..1..1..2..2....0..1..1..2..2....1..1..1..1..1....0..1..1..2..2
%e A201270 ..0..1..1..2..2....0..1..1..2..2....1..2..2..2..2....1..1..1..2..2
%e A201270 ..1..1..1..2..2....1..1..1..2..2....2..2..2..2..2....1..1..1..2..2
%Y A201270 Main diagonal of A201277.
%K A201270 nonn
%O A201270 0,2
%A A201270 _R. H. Hardin_, Nov 29 2011
%E A201270 a(0)=1 prepended and a(19)-a(23) added by _Alois P. Heinz_, Mar 17 2024

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