Really big deck
Your calculation is not accounting for the effect of removal of the first card in your hand (If you get a ten as your first card, the odds are now slightly better to get an Ace as your second, since you are now drawing from a smaller deck with 1 fewer non-ace cards, for example.)
Your answer of .0473 is correct for an infinite deck (or drawing with replacement.)
Chances of getting a blackjack:
4.827% one deck
4.779% two decks
4.757% four decks
4.734% infinite deck
This decreasing likelyhood of getting a blackjack is partially why the house edge increases as number of decks increases even if the game has identical rules.