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A211808 Rectangular array: R(k,n) = number of ordered triples (w,x,y) with all terms in {1,...,n} and 2w^k<=x^k+y<k. 5

%I #5 Dec 04 2016 19:46:28

%S 1,5,1,16,5,1,36,16,5,1,69,36,16,5,1,117,69,38,16,5,1,184,119,73,38,

%T 16,5,1,272,190,123,75,38,16,5,1,385,282,194,131,75,38,16,5,1,525,399,

%U 290,204,131,75,38,16,5,1,696,547,415,300,210,131,75,38,16,5,1

%N Rectangular array: R(k,n) = number of ordered triples (w,x,y) with all terms in {1,...,n} and 2w^k<=x^k+y<k.

%C Row 1: A055232

%C Row 2: A211806

%C Row 3: A211807

%C Limiting row sequence: A000330

%C Let R be the array in A211808 and let R' be the array in A182259. Then R(k,n)+R'(k,n)=3^(n-1).

%C See the Comments at A211790.

%e Northwest corner:

%e 1...5...16...36...69...117...184

%e 1...5...16...36...69...119...190

%e 1...5...16...38...73...123...194

%e 1...5...16...38...75...131...204

%e 1...5...16...38...75...131...210

%t z = 48;

%t t[k_, n_] := Module[{s = 0},

%t (Do[If[2 w^k <= x^k + y^k, s = s + 1],

%t {w, 1, #}, {x, 1, #}, {y, 1, #}] &[n]; s)];

%t Table[t[1, n], {n, 1, z}] (* A055232 *)

%t Table[t[2, n], {n, 1, z}] (* A211806 *)

%t Table[t[3, n], {n, 1, z}] (* A211807 *)

%t TableForm[Table[t[k, n], {k, 1, 12}, {n, 1, 16}]]

%t Flatten[Table[t[k, n - k + 1],

%t {n, 1, 12}, {k, 1, n}]] (* A211808 *)

%t Table[k (4 k^2 - 3 k + 5)/6,

%t {k, 1, z}] (* row-limit sequence, A174723 *)

%t (* _Peter J. C. Moses_, Apr 13 2012 *)

%Y Cf. A211790.

%K nonn,tabl

%O 1,2

%A _Clark Kimberling_, Apr 22 2012

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Last modified April 24 09:42 EDT 2024. Contains 371935 sequences. (Running on oeis4.)