A simple (though somewhat pedantic) question: when using big O notation in a sentence, should it be preceded with a or an?  Example:The extra loop results in a/an $\mathcal{O}(N)$ increase in cost.The ubiquitous Cormen textbook notes on page 47:For a given function $g(n)$, we denote by $\mathcal{O}(g(n))$ (pronounced big-oh of g of n or sometimes just oh of g of n)which would seem to indicate a should precede something pronounced big-oh.  Later on the same page, however, the textbook uses the phrase an $\mathcal{O}(n^2)$ upper bound.   Which is used more in the literature?  It seems like a triviality, but as someone working on the edge of theoretical computer science from a primary focus on another field, I'd like not to sound like an outsider. 
a or an with big O notation?
notation
Evidence for an:Ajtai, Mikls, Jnos Komls, and Endre Szemerdi. An O(n log n) sorting network. Proceedings of the fifteenth annual ACM symposium on Theory of computing. ACM, 1983.Asadpour, Arash, et al. An O(log n/log log n)-approximation Algorithm for the Asymmetric Traveling Salesman Problem. SODA. Vol. 10. 2010.Bracha, Gabriel. An O(log n) expected rounds randomized Byzantine generals protocol. Journal of the ACM (JACM) 34.4 (1987): 910-920.Hwang, F. K. An O(n log n) algorithm for suboptimal rectilinear Steiner trees. Circuits and Systems, IEEE Transactions on 26.1 (1979): 75-77.Tarjan, Robert E., and Christopher J. Van Wyk. An O(n log log n)-time algorithm for triangulating a simple polygon. SIAM Journal on Computing 17.1 (1988): 143-178.Yao, Andrew Chi-Chih. An O (|E| log log|V|) algorithm for finding minimum spanning trees. Information Processing Letters 4.1 (1975): 21-23.Of course, these examples alone merely suggest that an is acceptable. This list does not show that an is necessarily standard or preferred nor does it show that a is unacceptable.