|
|
A100437
|
|
Number of distinct products i*j*k*l for 1 <= i <= j <= k <= l <= n.
|
|
5
|
|
|
1, 5, 15, 25, 55, 75, 140, 175, 225, 275, 448, 504, 770, 882, 1022, 1134, 1626, 1782, 2460, 2670, 2970, 3270, 4345, 4565, 5135, 5585, 6100, 6505, 8338, 8679, 10927, 11525, 12393, 13261, 14345, 14787, 18187, 19344, 20618, 21346, 25823, 26698
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
MAPLE
|
f:=proc(n) local i, j, k, l, t1; t1:={}; for i from 1 to n do for j from i to n do for k from j to n do for l from k to n do t1:={op(t1), i*j*k*l}; od: od: od: od: t1:=convert(t1, list); nops(t1); end;
|
|
MATHEMATICA
|
f[n_] := Length[ Union[ Flatten[ Table[ i*j*k*l, {i, n}, {j, i, n}, {k, j, n}, {l, k, n}] ]]]; Table[ f[n], {n, 45}] (* Robert G. Wilson v, Dec 14 2004 *)
|
|
PROG
|
(PARI) pr(n)=my(v=List()); for(i=1, n, for(j=i, n, listput(v, i*j))); Set(v)
a(n)=my(u=List(), v=pr(n)); for(i=1, #v, for(j=i, #v, listput(u, v[i]*v[j]))); #Set(u) \\ Charles R Greathouse IV, Mar 04 2014
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|