Krenko doubles your Goblins, then Skirk Prospector sacrifices Krenko and enough Goblins to recast it, tax included. With Goblins minus tax at 5 the loop makes two more Goblins each time, as fast as the tax grows; above that it grows faster and faster, below it dies out.
Goblins needed7with commander tax
The loop grows every timeArbitrarily many Goblins, two more each loop, as the tax grows by .
7 of 7 Goblins
Goblins, step by step
1001020304050
To start: 7 GoblinsTo start: 7 Goblins0
Krenko taps: 14 GoblinsKrenko taps: 14 Goblins1
Sacrifice 6, Krenko included, to recast it for : 9 GoblinsSacrifice 6, Krenko included, to recast it for : 9 Goblins2
Krenko taps: 18 GoblinsKrenko taps: 18 Goblins3
Sacrifice 8, Krenko included, to recast it for : 11 GoblinsSacrifice 8, Krenko included, to recast it for : 11 Goblins4
Krenko taps: 22 GoblinsKrenko taps: 22 Goblins5
Sacrifice 10, Krenko included, to recast it for : 13 GoblinsSacrifice 10, Krenko included, to recast it for : 13 Goblins6
Krenko taps: 26 GoblinsKrenko taps: 26 Goblins7
Sacrifice 12, Krenko included, to recast it for : 15 GoblinsSacrifice 12, Krenko included, to recast it for : 15 Goblins8
Krenko taps: 30 GoblinsKrenko taps: 30 Goblins9
Sacrifice 14, Krenko included, to recast it for : 17 GoblinsSacrifice 14, Krenko included, to recast it for : 17 Goblins10
Krenko taps: 34 GoblinsKrenko taps: 34 Goblins11
Sacrifice 16, Krenko included, to recast it for : 19 GoblinsSacrifice 16, Krenko included, to recast it for : 19 Goblins12
Krenko taps: 38 GoblinsKrenko taps: 38 Goblins13
Sacrifice 18, Krenko included, to recast it for : 21 GoblinsSacrifice 18, Krenko included, to recast it for : 21 Goblins14
Krenko taps: 42 GoblinsKrenko taps: 42 Goblins15
Sacrifice 20, Krenko included, to recast it for : 23 GoblinsSacrifice 20, Krenko included, to recast it for : 23 Goblins16