как сумму арифметической прогрессии с определенным шагом

[рони]

Nexus,
для варианта пост №8
min,max,step, fn, test, test == fn
-5,8,9,12,-1,false
5,7,4,14,5,false
7,9,18,32,7,false
-1,18,1,170,170,true
9,34,4,184,147,false
4,9,16,24,4,false
-4,21,18,42,10,false
-7,20,18,33,4,false
8,33,29,45,8,false
-2,17,12,30,8,false
-2,12,26,22,-2,false
5,18,9,42,19,false
-1,22,18,51,16,false
9,19,24,42,9,false
3,15,2,63,63,true
7,27,13,60,27,false
-7,13,1,63,63,true
-5,21,2,112,112,true
0,7,9,9,0,false
5,33,21,78,31,false
2,9,28,32,2,false
0,11,27,27,0,false
-9,13,24,6,-9,false
9,30,1,429,429,true
-2,17,17,45,13,false
4,32,1,522,522,true
-4,21,7,50,26,false
8,14,20,36,8,false
3,7,29,35,3,false
8,37,9,130,86,false
3,8,24,30,3,false
0,28,18,54,18,false
-3,13,4,25,25,true
2,29,8,90,56,false
-4,5,27,19,-4,false
5,9,24,34,5,false
-9,2,3,-15,-18,false
-5,23,5,70,45,false
7,21,11,54,25,false
9,33,2,273,273,true
4,31,26,90,34,false
8,28,16,72,32,false
-6,19,2,98,78,false
-2,-2,11,-2,-2,true
8,9,3,19,8,false
-7,22,27,60,13,false
-4,16,20,12,12,true
-5,3,13,3,-5,false
-8,1,27,11,-8,false
-9,16,18,27,0,false
1,15,9,30,11,false
5,8,28,38,5,false
8,29,2,228,198,false
0,2,21,21,0,false
4,23,10,42,18,false
4,5,3,11,4,false
-5,19,1,175,175,true
7,27,24,38,7,false
1,5,25,27,1,false
-3,4,1,4,4,true
-3,1,3,0,-3,false
0,3,14,14,0,false
3,8,27,33,3,false
-4,19,3,72,52,false
-8,-2,26,10,-8,false
-3,20,15,36,9,false
1,5,12,14,1,false
6,26,2,176,176,true
-1,7,1,27,27,true
0,19,14,42,14,false
-5,-5,20,-5,-5,true
-1,10,4,20,9,false
-6,-3,1,-18,-18,true
3,31,29,35,3,false
6,22,1,238,238,true
4,29,15,57,23,false
3,5,15,21,3,false
-1,11,22,20,-1,false
-6,15,14,24,2,false
5,9,24,34,5,false
1,1,17,1,1,true
7,23,1,255,255,true
-7,17,29,15,-7,false
6,34,1,580,580,true
-6,22,18,36,6,false
0,13,18,18,0,false
-9,8,13,12,-5,false
9,31,10,96,57,false
0,21,24,24,0,false
0,16,26,26,0,false
-5,9,20,10,-5,false
-9,19,25,48,7,false
-1,10,7,18,5,false
-7,21,11,38,12,false
8,12,10,26,8,false
4,14,1,99,99,true
-4,-1,11,3,-4,false
-7,6,17,3,-7,false
8,10,17,33,8,false
1,2,11,13,1,false

[рони]

так, вроде бы, правильно

для варианта пост №10

-8,11,20,-8,-8,true
3,11,12,3,3,true
-4,17,22,-4,-4,true
3,27,17,23,23,true
-7,8,1,8,8,true
-6,23,20,8,8,true
5,23,17,27,27,true
7,8,5,7,7,true
-7,-4,27,-7,-7,true
-5,23,21,11,11,true
-5,19,18,8,8,true
9,23,5,42,42,true
2,11,10,2,2,true
2,6,1,20,20,true
0,0,25,0,0,true
-7,12,28,-7,-7,true
-2,12,10,6,6,true
2,24,25,2,2,true
-9,7,3,-9,-9,true
2,20,8,30,30,true
-9,-6,10,-9,-9,true
6,26,17,29,29,true
-7,22,23,9,9,true
-1,3,17,-1,-1,true
-3,22,3,81,81,true
8,14,17,8,8,true
8,35,17,33,33,true
4,28,14,22,22,true
6,7,2,6,6,true
6,7,18,6,6,true
7,11,13,7,7,true
4,31,22,30,30,true
5,24,20,5,5,true
4,29,29,4,4,true
-7,2,19,-7,-7,true
-8,-4,18,-8,-8,true
0,4,8,0,0,true
-1,3,25,-1,-1,true
6,22,16,28,28,true
6,17,1,138,138,true
-8,-3,25,-8,-8,true
2,25,20,24,24,true
-6,20,7,18,18,true
-7,8,16,-7,-7,true
-3,8,22,-3,-3,true
3,21,29,3,3,true
8,21,3,70,70,true
8,16,29,8,8,true
3,31,1,493,493,true
-7,14,26,-7,-7,true
5,13,28,5,5,true
-2,27,29,25,25,true
3,26,26,3,3,true
-9,10,16,-2,-2,true
4,9,11,4,4,true
6,7,24,6,6,true
1,16,1,136,136,true
7,8,1,15,15,true
-1,24,23,21,21,true
9,34,21,39,39,true
-7,19,19,5,5,true
8,25,24,8,8,true
-5,7,14,-5,-5,true
0,10,13,0,0,true
-2,26,6,50,50,true
3,10,23,3,3,true
1,8,12,1,1,true
0,24,24,24,24,true
7,9,7,7,7,true
-8,5,16,-8,-8,true
3,28,22,28,28,true
-5,7,22,-5,-5,true
-4,20,4,56,56,true
-4,-1,5,-4,-4,true
5,27,8,39,39,true
0,17,28,0,0,true
-8,5,14,-8,-8,true
0,26,15,15,15,true
5,6,23,5,5,true
-7,9,22,-7,-7,true
-4,20,1,200,200,true
7,33,7,70,70,true
-2,17,29,-2,-2,true
0,23,4,60,60,true
-4,4,17,-4,-4,true
4,29,23,31,31,true
7,9,24,7,7,true
-3,11,15,-3,-3,true
7,21,6,39,39,true
-4,12,20,-4,-4,true
-1,13,9,7,7,true
7,7,4,7,7,true
6,19,10,22,22,true
-4,14,15,7,7,true
-4,6,26,-4,-4,true
-2,6,9,-2,-2,true
2,24,25,2,2,true
-4,6,13,-4,-4,true
8,30,4,108,108,true
-9,-2,6,-12,-12,true

[рони]

Nexus,
почти одинаковый код у нас,
я только убрал все числа, кроме одного из кода.
(исключительно по желанию, результат выше уже достаточен)

[рони]

Nexus,

function fun(min, max, step) {
  var n = (max - min) / step | 0;
  return (min + n * step / 2) * ++n;
};
alert(fun(9,15,5));

[Nexus]

рони,