login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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
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, 16, 5, 1, 272, 190, 123, 75, 38, 16, 5, 1, 385, 282, 194, 131, 75, 38, 16, 5, 1, 525, 399, 290, 204, 131, 75, 38, 16, 5, 1, 696, 547, 415, 300, 210, 131, 75, 38, 16, 5, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 1:  A055232

Row 2:  A211806

Row 3:  A211807

Limiting row sequence: A000330

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).

See the Comments at A211790.

LINKS

Table of n, a(n) for n=1..66.

EXAMPLE

Northwest corner:

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

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

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

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

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

MATHEMATICA

z = 48;

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

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

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

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

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

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

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

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

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

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

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

(* Peter J. C. Moses, Apr 13 2012 *)

CROSSREFS

Cf. A211790.

Sequence in context: A019429 A221364 A211805 * A093826 A144699 A066787

Adjacent sequences:  A211805 A211806 A211807 * A211809 A211810 A211811

KEYWORD

nonn,tabl

AUTHOR

Clark Kimberling, Apr 22 2012

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 6 07:02 EDT 2020. Contains 333267 sequences. (Running on oeis4.)