expand seems not correct

[AmplitudeGravity]

big(3)^100 

is 515377520732011331036461129765621272702107522001

then I tried Symbolics, it get different result.

using Symbolics
@variables x y
f=expand((x+y)^100);
substitute(f,Dict(x => big(1),y=> big(2)))

the output is 82584274084965915071296193740091271394366417

strange!
BTW, expand((x+y)^50) works

┆Issue is synchronized with this Trello card by Unito

[shashi]

Seems to be integer overflow in DynamicPolynomials...

julia> @polyvar x y
(x, y)

julia> p = (x+y)^100

has negative coefficients.

I wish it handled this automatically because SymbolicUtils does not see the process where an integer grows too big for Int.

cc @blegat