A119867 Number of different values assumed by a*b+c*d as a,b,c,d range between 1 and n.

1, 6, 14, 25, 40, 57, 79, 103, 132, 165, 201, 239, 283, 329, 379, 434, 493, 554, 620, 688, 762, 839, 918, 1000, 1089, 1182, 1277, 1376, 1480, 1586, 1698, 1811, 1930, 2051, 2175, 2306, 2441, 2577, 2717, 2860, 3010, 3162, 3320, 3479, 3643, 3812, 3983, 4156

Offset

1,2

Links

Donovan Johnson, Table of n, a(n) for n = 1..500

Example

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

Mathematica

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

Crossrefs

Cf. A119868.

Sequence in context: A010740 A185594 A095794 * A293400 A026055 A288939

Adjacent sequences: A119864 A119865 A119866 * A119868 A119869 A119870

Keyword

nonn

Author

Giovanni Resta, May 26 2006

Status

approved