cp's OEIS Frontend

A027426 Number of distinct products ijk with 0 <= i,j,k <= n.

%I A027426 #29 May 28 2021 23:03:20
%S A027426 1,2,5,11,17,31,41,66,81,101,121,174,195,267,302,344,379,493,537,679,
%T A027426 733,805,877,1076,1131,1248,1344,1451,1538,1834,1910,2249,2363,2516,
%U A027426 2669,2851,2941,3401,3588,3790,3920,4478,4625,5243,5441,5655,5917,6647,6799,7197
%N A027426 Number of distinct products ijk with 0 <= i,j,k <= n.
%H A027426 Alois P. Heinz, <a href="/A027426/b027426.txt">Table of n, a(n) for n = 0..1000</a> (first 201 terms from T. D. Noe)
%F A027426 a(n) = A027425(n) + 1. - _T. D. Noe_, Jan 16 2007
%p A027426 a:=proc(n): nops({seq(seq(seq(i*j*k,k=0..j),j=0..i),i=0..n)}) end: seq(a(n),n=0..50); # _Emeric Deutsch_, Jan 25 2007
%t A027426 a[n_] := Table[i*j*k, {i, 0, n}, {j, i, n}, {k, j, n}] // Flatten // Union // Length; Table[a[n], {n, 0, 50}] (* _Jean-François Alcover_, Jan 30 2018 *)
%o A027426 (Haskell)
%o A027426 import Data.List (nub)
%o A027426 a027426 n = length $ nub [i*j*k | i <- [0..n], j <- [0..n], k <- [0..n]]
%o A027426 -- _Reinhard Zumkeller_, Jan 01 2012
%o A027426 (PARI) pr(n)=my(v=List());for(i=1,n, for(j=i,n, listput(v, i*j))); Set(v)
%o A027426 a(n)=my(v=pr(n),u=v); for(i=2,n,u=Set(concat(u,v*i))); #u+1 \\ _Charles R Greathouse IV_, Mar 04 2014
%o A027426 (Python)
%o A027426 from itertools import combinations_with_replacement as mc
%o A027426 def a(n): return len(set(i*j*k for i, j, k in mc(range(n+1), 3)))
%o A027426 print([a(n) for n in range(50)]) # _Michael S. Branicky_, May 28 2021
%Y A027426 Cf. A027384, A027429.
%K A027426 nonn
%O A027426 0,2
%A A027426 _N. J. A. Sloane_