A083505 Erroneous version of A027428.
1, 3, 6, 10, 14
Offset: 2
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import Data.List (nub) a027430 n = length $ nub [i*j*k | k<-[3..n], j<-[2..k-1], i<-[1..j-1]] -- Reinhard Zumkeller, Jan 01 2012
nn = 50;
prod = Table[0, {1 + nn^3}];
a[1] = 0;
a[n_] := (Do[prod[[1 + i*j*k]] = 1, {i, 0, n}, {j, i+1, n}, {k, j+1, n}]; Count[Take[prod, 1 + n^3], 1] - 1);
Array[a, nn] (* Jean-François Alcover, Jul 31 2018, after T. D. Noe *)
\\ See PARI link. David A. Corneth, Jul 31 2018
def A027430(n): return len({i*j*k for i in range(1,n+1) for j in range(1,i) for k in range(1,j)}) # Chai Wah Wu, Oct 16 2023
f:=proc(n) local i,j,k,t1; t1:={}; for i from 1 to n-1 do for j from i to n-1 do for k from j+1 to n do t1:={op(t1),i*j*k}; od: od: od: t1:=convert(t1,list); nops(t1); end;
f[n_] := Length[ Union[ Flatten[ Table[ i*j*k, {i, n}, {j, i, n}, {k, j + 1, n}] ]]]; Table[ f[n], {n, 49}] (* Robert G. Wilson v, Dec 14 2004 *)
def A100435(n): return len({i*j*k for i in range(1,n+1) for j in range(1,i) for k in range(1,j+1)}) # Chai Wah Wu, Oct 16 2023
import Data.List (nub) a027427 n = length $ nub [i*j | j <- [1..n], i <- [0..j-1]] -- Reinhard Zumkeller, Jan 01 2012
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
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 *)
def A027427(n): return 1+len({i*j for i in range(1,n+1) for j in range(1,i)}) if n else 0 # Chai Wah Wu, Oct 13 2023
2 2,3,6 2,3,4,6,8,12 2,3,4,5,6,8,10,12,15,20 2,3,4,5,6,8,10,12,15,16,18,20,24,30 2,3,4,5,6,7,8,10,12,... ...