Fix doc rendering issue for power numbers

Author: joaquim-verges

contracts/eip/ERC721A.sol

@@ -17,9 +17,9 @@ import "./ERC165.sol";
  *
  * Assumes serials are sequentially minted starting at _startTokenId() (defaults to 0, e.g. 0, 1, 2, 3..).
  *
- * Assumes that an owner cannot have more than 2**64 - 1 (max value of uint64) of supply.
+ * Assumes that an owner cannot have more than 2^64 - 1 (max value of uint64) of supply.
  *
- * Assumes that the maximum token id cannot exceed 2**256 - 1 (max value of uint256).
+ * Assumes that the maximum token id cannot exceed 2^256 - 1 (max value of uint256).
  */
 contract ERC721A is Context, ERC165, IERC721A {
     using TWAddress for address;

docs/ERC721A.md

@@ -6,7 +6,7 @@
 
 
 
-*Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including the Metadata extension. Built to optimize for lower gas during batch mints. Assumes serials are sequentially minted starting at _startTokenId() (defaults to 0, e.g. 0, 1, 2, 3..). Assumes that an owner cannot have more than 2**64 - 1 (max value of uint64) of supply. Assumes that the maximum token id cannot exceed 2**256 - 1 (max value of uint256).*
+*Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including the Metadata extension. Built to optimize for lower gas during batch mints. Assumes serials are sequentially minted starting at _startTokenId() (defaults to 0, e.g. 0, 1, 2, 3..). Assumes that an owner cannot have more than 2^64 - 1 (max value of uint64) of supply. Assumes that the maximum token id cannot exceed 2^256 - 1 (max value of uint256).*
 
 ## Methods