Summations on Variables with subscripts

Question

One of my equations uses a set of variables which ultimately for a set of certain values gives a list of 8 numbers: c=13.9506 (31 - k) following cc(sub k) = Round[Table[13.950621339931203(31 - k), {k, 1, 8, 1}]] Results in the following List {419, 405, 391, 377, 363, 349, 335, 321} which feeds another equation with summation: **My problem is that the final Variable cc with a subscript k, when its used in the bellow summation it DOES not consider each element of the list as vector Instead it leaves the element as it is!! WHAT SHOULD I DO in order when the summation sees cc subscript 1 to use the value of 419, cc(sub 2) the value of 405 (but without denote each var separately)** enter code here`tc = !( *UnderoverscriptBox[([Sum]), (k = 1), (depo)]( *SuperscriptBox[((1 + wacc)), (-k)] *SubscriptBox[(cc), (k)]))`` Forgive my ignorance and thank y in advance.

Please consider that I need to use the subscript and not use loops of if. A similar example of my problem can be seen in the picture attached where the summation doesnot count the values of the list according to subscript

Answer 1

I'm not sure what you're asking and I'm aware subscripts are discouraged but I've used them with success. First clear them out with the assignment $a_n=.$, then assign them, then can use like any other variable. Can even use a (integer) function as the subscript like $a_{f(n)}$. Keep in mind when using functions as subscripts, some of the variables will either not be assigned or have previous values. In the case below using myIntegerF[n] as the subscript, $a_1$ through $a_5$ have not been assigned or if not cleared out first will have the old values. Need to pay attention to this. Also, when I typed in this code in Mathematica I used the [ctrl] underscore key to input a formatted subscripted variable so don't have to use the function Subscript[a,n] below (it was not converted when I cut and pasted it).

Quiet@Table[Subscript[a, n] =., {n, 1, 100}];
Table[Subscript[a, n] = n, {n, 1, 100}]
Sum[Subscript[a, n], {n, 1, 100}]
Quiet@Table[Subscript[a, n] =., {n, 1, 100}];
myIntegerF[n_] := 2 n + 4;
Table[Subscript[a, myIntegerF[n]] = n, {n, 1, 10}]
Table[Subscript[a, n], {n, 1, 24}]

Answer 2

Regarding your last comment, how about assigning each subscripted variable a list like $v_1=\{2,3,4\}$, then $(v_1)^3=\{4,9,16\}$. So we could code:

Table[Subscript[v, i] =., {i, 1, 100}]
Table[Subscript[v, 
  i] = {RandomInteger[{1, 10}], RandomInteger[{1, 10}], 
   RandomInteger[{1, 10}]}, {i, 1, 10}]
Plus@@Sum[Subscript[v, i]^3, {i, 1, 10}]