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 A027427 Number of distinct products ij with 0 <= i < j <= n. 4
 0, 1, 2, 4, 7, 11, 14, 20, 25, 32, 37, 47, 52, 64, 71, 79, 88, 104, 112, 130, 140, 151, 162, 184, 193, 211, 224, 240, 253, 281, 292, 322, 338, 355, 372, 391, 404, 440, 459, 479, 494, 534, 550, 592, 612, 632, 655, 701, 718, 753, 775, 801, 824, 876 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS T. D. Noe, Table of n, a(n) for n = 0..1000 FORMULA a(n)=A027428(n)+1. - T. D. Noe, Jan 16 2007 MAPLE A027427 := proc(n)     local L, i, j ;     L := {};     for i from 0 to n do         for j from i+1 to n do             L := L union {i*j};         end do:     end do:     nops(L); end proc:  # R. J. Mathar, Jun 09 2016 MATHEMATICA a[n_] := Table[i*j, {i, 0, n}, {j, i+1, n}] // Flatten // Union // Length; Table[a[n], {n, 0, 60}] (* Jean-François Alcover, Feb 03 2018 *) PROG (Haskell) import Data.List (nub) a027427 n = length \$ nub [i*j | j <- [1..n], i <- [0..j-1]] -- Reinhard Zumkeller, Jan 01 2012 CROSSREFS Cf. A027430, etc. Cf. A027384, A027429. Sequence in context: A054850 A225154 A167805 * A306070 A262136 A330822 Adjacent sequences:  A027424 A027425 A027426 * A027428 A027429 A027430 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 25 23:23 EDT 2020. Contains 337346 sequences. (Running on oeis4.)