a+(n-1)*4
49, 64, 81
1 x 2 sqrt(4) = 4
106------------------------------------------------------------------------------------------------From Rafaelrz.You can make, 4P3 = 4!/(4-3)! = 24, different 3 digit numbers using 1, 2, 3 and 4.
1124 1224 1244
1, 2, 4, 61, 122 and 244.
a+(n-1)*4
1 x 244, 2 x 122, 4 x 61 61 x 4, 122 x 2, 244 x 1
49, 64, 81
4 + 3 x (2 - 1)
1 x 2 sqrt(4) = 4
61 ÷ 4 = 15 with remainder 1
4*4*4 = 64 of them.
106------------------------------------------------------------------------------------------------From Rafaelrz.You can make, 4P3 = 4!/(4-3)! = 24, different 3 digit numbers using 1, 2, 3 and 4.
.1 + .2 + .3 + .4 = 1
1124 1224 1244
The numbers are 57, 59, 61 and 63.