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 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 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

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