fix bug in seed calculation

Author: linoscope

specs/fulu/beacon-chain.md

@@ -163,9 +163,9 @@ def compute_proposer_indices(state: BeaconState, epoch: Epoch) -> List[Validator
     """
     Return the proposer indices for the given `epoch`.
     """
-    start_seed = get_seed(state, epoch, DOMAIN_BEACON_PROPOSER) + uint_to_bytes(compute_start_slot_at_epoch(epoch))
-    seeds = [hash(start_seed + uint_to_bytes(Slot(i))) for i in range(SLOTS_PER_EPOCH)]
+    epoch_seed = get_seed(state, epoch, DOMAIN_BEACON_PROPOSER)
     indices = get_active_validator_indices(state, epoch)
+    seeds = [hash(epoch_seed + uint_to_bytes(Slot(i))) for i in range(SLOTS_PER_EPOCH)]
     return [compute_proposer_index(state, indices, seed) for seed in seeds]
 ```
 
@@ -235,4 +235,4 @@ def process_proposer_lookahead(state: BeaconState) -> None:
     # Fill in the last epoch with new proposer indices
     last_epoch_proposers = compute_proposer_indices(state, Epoch(get_current_epoch(state) + MIN_SEED_LOOKAHEAD + 1))
     state.proposer_lookahead[last_epoch_start:] = last_epoch_proposers
-```
+```