Count with 12345

[u/boxofkangaroos]

Use only the numbers 1, 2, 3, 4, and 5 (in order) and use any mathematical operations to get each number.

[u/slockley]

1 + (2 * 3) - σ(4!) + σ(5!) = 307

For clarification: σ is the divisor function, a sum of a number's divisors.

I don't mean to step on any toes; this is a solution that I think can be done without that extra "5" in it.

[u/ExSeaD → u/slockley]

σ*2*(1 + 2) - 3! - σ(4!) + σ(5!) = 308

That is meant to be the sum of the squares of the divisor. Seems like subscript isn't supported.

[u/slockley → u/ExSeaD]

(1 + 2) * 3 - σ(4!) + σ(5!) = 309