Continuous formula drawing?

Question

WolframAlpha is good and all.

But do you know a website that could "Brute Force" formula? A site that could turn 20 + 5a into:

a=1   25
a=2   30
a=3   35
a=4   40

Of course I could calculate myself, but sometimes I come on formulas that I need few minutes to expand with this method, while computer possibly can do it within seconds.

Answer 1

Wolfram Alpha can actually do that. For example, say you wanted a table of $a^2+a-2$ for $a=1,2,3,\cdots, 11$ but didn't want to do it by hand. Go to Wolfram Alpha and enter

Table[a^2+a-2,{a,1,11}]

The format will always be

Table[ formula you want to calculate in terms of a,
 {a,smallest a, largest a}]

Moreover, if you only wanted the even $a$'s for example, then you would have entered

Table[a^2+a-2,{a,1,11,2}]

The last number, in this case $2$, tells what to increase $a$ by each time. So there it says to start at $a=1$ then add $2$ each time until $a$ is no bigger than $11$.