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Description: The value of the divisor function. (Contributed by Mario Carneiro, 22-Sep-2014) (Revised by Mario Carneiro, 21-Jun-2015)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | sgmval | |- ( ( A e. CC /\ B e. NN ) -> ( A sigma B ) = sum_ k e. { p e. NN | p || B } ( k ^c A ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | simpr | |- ( ( x = A /\ n = B ) -> n = B ) |
|
| 2 | 1 | breq2d | |- ( ( x = A /\ n = B ) -> ( p || n <-> p || B ) ) |
| 3 | 2 | rabbidv | |- ( ( x = A /\ n = B ) -> { p e. NN | p || n } = { p e. NN | p || B } ) |
| 4 | simpll | |- ( ( ( x = A /\ n = B ) /\ k e. { p e. NN | p || n } ) -> x = A ) |
|
| 5 | 4 | oveq2d | |- ( ( ( x = A /\ n = B ) /\ k e. { p e. NN | p || n } ) -> ( k ^c x ) = ( k ^c A ) ) |
| 6 | 3 5 | sumeq12dv | |- ( ( x = A /\ n = B ) -> sum_ k e. { p e. NN | p || n } ( k ^c x ) = sum_ k e. { p e. NN | p || B } ( k ^c A ) ) |
| 7 | df-sgm | |- sigma = ( x e. CC , n e. NN |-> sum_ k e. { p e. NN | p || n } ( k ^c x ) ) |
|
| 8 | sumex | |- sum_ k e. { p e. NN | p || B } ( k ^c A ) e. _V |
|
| 9 | 6 7 8 | ovmpoa | |- ( ( A e. CC /\ B e. NN ) -> ( A sigma B ) = sum_ k e. { p e. NN | p || B } ( k ^c A ) ) |