Nitric acid does not form the anhydride but dinitrogen penta oxide is theoretical anhydride of nitric acid.
2HNO3 = N2O5 + H2O
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No. From the Wikipedia article on nitrogen pentoxide:
N2O5 was first reported by Deville in 1840, who prepared it by treating AgNO3 with Cl2.
Therefore, nitrogen pentoxide is the anhydride of nitric acid.