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A027425 Number of distinct products ijk with 1 <= i,j,k <= n. 13
1, 4, 10, 16, 30, 40, 65, 80, 100, 120, 173, 194, 266, 301, 343, 378, 492, 536, 678, 732, 804, 876, 1075, 1130, 1247, 1343, 1450, 1537, 1833, 1909, 2248, 2362, 2515, 2668, 2850, 2940, 3400, 3587, 3789, 3919, 4477, 4624, 5242, 5440, 5654, 5916 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..1000 (first 200 terms from T. D. Noe)

FORMULA

a(n) = A027426(n)-1. - T. D. Noe, Jan 16 2007

MAPLE

f:=proc(n) local i, j, k, t1, t2; t1:={}; for i from 1 to n do for j from i to n do for k from j to n do t1:={op(t1), i*j*k}; od: od: od: t1:=convert(t1, list); nops(t1); end;

MATHEMATICA

a[n_] := Reap[Do[Sow[i*j*k], {i, 1, n}, {j, i, n}, {k, j, n}]][[2, 1]] // Union // Length; Table[a[n], {n, 1, 50}] (* Jean-Fran├žois Alcover, Jan 30 2018 *)

PROG

(Haskell)

import Data.List (nub)

a027425 n = length $ nub [i*j*k | i <- [1..n], j <- [1..n], k <- [1..n]]

-- Reinhard Zumkeller, Jan 01 2012

(PARI) pr(n)=my(v=List()); for(i=1, n, for(j=i, n, listput(v, i*j))); Set(v)

a(n)=my(v=pr(n), u=v); for(i=2, n, u=Set(concat(u, v*i))); #u \\ Charles R Greathouse IV, Mar 04 2014

CROSSREFS

Cf. A027424, A027426, A027430.

Sequence in context: A167346 A027430 A298031 * A024992 A224966 A069982

Adjacent sequences:  A027422 A027423 A027424 * A027426 A027427 A027428

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified March 26 23:02 EDT 2019. Contains 321565 sequences. (Running on oeis4.)