login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A245556 Irregular triangle read by rows: T(n,k) (n>=0, 0 <= k <= 2n) = number of triples (u,v,w) with entries in the range 0 to n which have some pair adding up to k. 3
1, 4, 6, 4, 7, 12, 19, 12, 7, 10, 18, 28, 36, 28, 18, 10, 13, 24, 37, 48, 61, 48, 37, 24, 13, 16, 30, 46, 60, 76, 90, 76, 60, 46, 30, 16, 19, 36, 55, 72, 91, 108, 127, 108, 91, 72, 55, 36, 19, 22, 42, 64, 84, 106, 126, 148, 168, 148, 126, 106, 84, 64, 42, 22 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..63.

EXAMPLE

Triangle begins:

[1]

[4, 6, 4]

[7, 12, 19, 12, 7]

[10, 18, 28, 36, 28, 18, 10]

[13, 24, 37, 48, 61, 48, 37, 24, 13]

[16, 30, 46, 60, 76, 90, 76, 60, 46, 30, 16]

[19, 36, 55, 72, 91, 108, 127, 108, 91, 72, 55, 36, 19]

[22, 42, 64, 84, 106, 126, 148, 168, 148, 126, 106, 84, 64, 42, 22]

...

See A245557 for specific examples; also the Example section of A090381 for some of the T(10,10)= 331 triples with n=k=10.

MAPLE

with(LinearAlgebra);

M:=10; A:=Array(0..M, 0..2*M); B:=Array(0..M, 0..2*M);

for n from 0 to M do

for i from 0 to n do for j from 0 to n do for k from 0 to n do

  s1:={i+j, i+k, j+k}; s1:=convert(s1, list); m1:=max(i, j, k);

    for r1 from 1 to nops(s1) do

       s:=s1[r1]; A[n, s] := A[n, s]+1;

       if (m1=n) then B[n, s] := B[n, s]+1; fi;

                              od:

od: od: od: od:

lprint("A245556");

for i from 0 to M do lprint([seq(A[i, j], j=0..2*i)]); od:

lprint("A245557");

for i from 0 to M do lprint([seq(B[i, j], j=0..2*i)]); od:

CROSSREFS

Rows are the partial sums of the rows of A245557.

Main "spine" of triangle is A090381.

Row sums are A005915.

Sequence in context: A181110 A199959 A084892 * A256318 A018835 A055166

Adjacent sequences:  A245553 A245554 A245555 * A245557 A245558 A245559

KEYWORD

nonn,tabf

AUTHOR

N. J. A. Sloane, Aug 04 2014

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 August 21 06:02 EDT 2019. Contains 326162 sequences. (Running on oeis4.)