A174413 Triangle T(n,m) with the denominator of 1/(n-m)^2-1/n^2, read by rows, 1<=m<n.

4, 36, 9, 144, 16, 16, 400, 225, 100, 25, 900, 144, 12, 9, 36, 1764, 1225, 784, 441, 196, 49, 3136, 576, 1600, 64, 576, 64, 64, 5184, 3969, 324, 2025, 1296, 81, 324, 81, 8100, 1600, 4900, 225, 100, 400, 900, 25, 100, 12100, 9801, 7744, 5929, 4356, 3025, 1936, 1089, 484, 121

Offset

2,1

Comments

Obtained by deleting the last entry in each row of A061036 or by reversing rows in A120073.

Links

Alois P. Heinz, Table of n, a(n) for n = 2..2017

Example

Triangle T(n,m) begins:
     4,
    36,    9,
   144,   16,   16,
   400,  225,  100,  25,
   900,  144,   12,   9,  36,
  1764, 1225,  784, 441, 196, 49,
  3136,  576, 1600,  64, 576, 64, 64,

Maple

A174413 := proc(n, m) 1/(n-m)^2-1/n^2 ; denom(%) ; end proc:
seq(seq(A174413(n, k), k=1..n-1), n=2..11); # R. J. Mathar, Jan 27 2011

Mathematica

T[n_, m_] := Denominator[1/(n - m)^2 - 1/n^2];
Table[T[n, m], {n, 2, 11}, {m, 1, n-1}] // Flatten (* Jean-François Alcover, May 18 2018 *)

Crossrefs

Cf. A165441, A172370 (numerators).

Sequence in context: A172282 A120083 A110219 * A162990 A366729 A092960

Adjacent sequences: A174410 A174411 A174412 * A174414 A174415 A174416

Keyword

nonn,frac,tabl,look,easy

Author

Paul Curtz, Mar 19 2010

Status

approved