login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

N. J. A. Sloane.

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