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A027420 Triangle T00, T10, T01, T20, T11, T02, etc., where Tmn = number of distinct products ij with min(m,n) <= i,j <= max(m,n). 3
1, 2, 2, 4, 1, 4, 7, 3, 3, 7, 10, 6, 1, 6, 10, 15, 9, 3, 3, 9, 15, 19, 14, 6, 1, 6, 14, 19, 26, 18, 10, 3, 3, 10, 18, 26, 31, 25, 14, 6, 1, 6, 14, 25, 31, 37, 30, 20, 10, 3, 3, 10, 20, 30, 37, 43, 36, 25, 15, 6, 1, 6, 15, 25, 36, 43, 54, 42, 31, 20, 10, 3, 3, 10, 20, 31, 42, 54 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

T(n,0) = T(n,n) = A027384(n). - Reinhard Zumkeller, May 02 2014

LINKS

Reinhard Zumkeller, Rows n = 0..125 of table, flattened

MATHEMATICA

t[m_, n_] := i*j /. {ToRules @ Reduce[ Min[m, n] <= i <= j <= Max[m, n], Integers]} // Union // Length; row[n_] := Table[ t[m, n-m], {m, 0, n} ]; Table[ row[n], {n, 0, 11}] // Flatten (* Jean-François Alcover, Apr 16 2013 *)

PROG

(Haskell)

import Data.List (nub)

a027420 n k = a027420_tabl !! n !! k

a027420_row n = a027420_tabl !! n

a027420_tabl = zipWith (zipWith z) a002262_tabl a025581_tabl

               where z u v = length $ nub $ [i * j | i <- zs, j <- zs]

                             where zs = [min u v .. max u v]

-- Reinhard Zumkeller, May 02 2014

CROSSREFS

Cf. A027384.

Cf. A241944 (row sums), A002262, A025581.

Sequence in context: A138558 A111580 A066202 * A116588 A069922 A072211

Adjacent sequences:  A027417 A027418 A027419 * A027421 A027422 A027423

KEYWORD

tabl,nonn,easy,nice

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Olivier Gérard, Nov 15 1997

STATUS

approved

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Last modified April 6 16:14 EDT 2020. Contains 333276 sequences. (Running on oeis4.)