Copyright ©2010 by Paul Niquette. All rights reserved.
are the only three letters that meet all 14 conditions
listed in the puzzle.
 Letters in the English alphabet are the same as those in the modern Latin or Roman alphabet but distinguished from the Archaic Latin alphabet: ABCDEFZHIKLMNOPQRSTVX.
 Letters formed with straight lines are readily discovered by grammar schoolers on the playgroud: AEFHIKLMNTVWXYZ.
 Letters formed without lifting pencil are likely indoor discoveries: CDIJLMNOPSUVWZ.
 Letters that take indefinite article "an" include all the vowels, of course, AEIOU (but not Y) along with certain consonants FLMNRSX.
 Letters pronounced with an initial "eh" are all consonants FLMNSX, decidedly not E.
 Consonants are plentiful BCDFGHJKLMNPQRSTVXZ plus Y and W most of the time.
 Consonants taking indefinite article "an" were included in  above FHLMNRSX.
 Consonants pronounced with an initial "eh" were included in  above FLMNSX.
 Consonants that are voiced are BDGJLMNRVWXYZ, some in order to distinguish them from other consonants: B|P, D|T, G|K, V|F, Z|S.
available for license-plates
produces an exhaustive count,
which combined with, say, four decimal digits means
that 10,000 vehicles
might wear LMN.
 Triads in alphabetical order having the same total as  may surprise some solvers. It assumes that [a] any triad can be put in alphabetical order and [b] XXX is in alphabetical order. For triads that can be selected from the alphabet in alphabetical order the number is 2,600.
 Triads in consecutive alphabetical order are as follows: ABC, BCD,...LMN,...WXY, XYZ.
 Triads that are abbreviations in real life were identified for LMN as follows:
Laboratory for Micro and Nanotechnology, lateral mammillary nucleus, lateral mesencephalic nucleus, Leadership and Management in Nursing, Legalize Marijuana Now, Lesbian Moms Network, library management network, Licium Multimedia Newsletter, Lifetime Movie Networks, Lio Marketing Network, Liquid Magnesium Networks, Little Miss Nicap, Livestock Monitor Newsletter, Local Media Network, Local Member Network, Local Model Networks, London Metropolitan Network, longitudinal motor neurones, Louisville Music News, low molecular nucleophilic substances, Lower Merion and Narberth, Lower Motor Neurons, Loyalty Management Netherlands, lupus membranous nephropathy, lymphoid and myeloid neoplasms.Bonus Puzzle
Which category in the table can be used to characterize exactly 13 of the first 100 integers.
Here they are: an eight, an eleven, an eighteen, an eighty, an eighty-one,... and an eighty-nine.
Now, if the word 'integer' were to be replaced with 'number', the total number of numbers would become infinite. The fraction of all numbers between 0 and 100 in such expressions as...