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%I #23 Oct 16 2023 23:29:21
%S 1,4,10,16,30,40,65,80,100,120,173,194,266,301,343,378,492,536,678,
%T 732,804,876,1075,1130,1247,1343,1450,1537,1833,1909,2248,2362,2515,
%U 2668,2850,2940,3400,3587,3789,3919,4477,4624,5242,5440,5654,5916
%N Number of distinct products ijk with 1 <= i,j,k <= n.
%H Alois P. Heinz, <a href="/A027425/b027425.txt">Table of n, a(n) for n = 1..1000</a> (first 200 terms from T. D. Noe)
%F a(n) = A027426(n)-1. - _T. D. Noe_, Jan 16 2007
%p 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;
%t 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-François Alcover_, Jan 30 2018 *)
%o (Haskell)
%o import Data.List (nub)
%o a027425 n = length $ nub [i*j*k | i <- [1..n], j <- [1..n], k <- [1..n]]
%o -- _Reinhard Zumkeller_, Jan 01 2012
%o (PARI) pr(n)=my(v=List());for(i=1,n, for(j=i,n, listput(v, i*j))); Set(v)
%o 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
%o (Python)
%o def A027425(n): return len({i*j*k for i in range(1,n+1) for j in range(1,i+1) for k in range(1,j+1)}) # _Chai Wah Wu_, Oct 16 2023
%Y Cf. A027424, A027426, A027430.
%K nonn
%O 1,2
%A _N. J. A. Sloane_.
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