A119867 - OEIS

%I #6 Feb 20 2013 05:10:19

%S 1,6,14,25,40,57,79,103,132,165,201,239,283,329,379,434,493,554,620,

%T 688,762,839,918,1000,1089,1182,1277,1376,1480,1586,1698,1811,1930,

%U 2051,2175,2306,2441,2577,2717,2860,3010,3162,3320,3479,3643,3812,3983,4156

%N Number of different values assumed by a*b+c*d as a,b,c,d range between 1 and n.

%H Donovan Johnson, <a href="/A119867/b119867.txt">Table of n, a(n) for n = 1..500</a>

%e a(2)=6 since we can obtain 6 values, i.e., {2, 3, 4, 5, 6, 8}.

%t Table[Length@Union@Flatten@Table[a*b + c*d, {a,n}, {b,n}, {c,n}, {d,n}], {n,24}]

%Y Cf. A119868.

%K nonn

%O 1,2

%A _Giovanni Resta_, May 26 2006