Counting rhymes -- Catalan, Bell numbers

     In mathematics, the Catalan numbers (named for Belgian mathematician Eugène Charles Catalan, 1814–1894, and beginning with 1, 1, 2, 5, 14, 42, 132, 429, . . . ) and the Bell numbers (named for the Scottish mathematician Eric Temple Bell, 1883-1960, and beginning with 1, 1, 2, 5, 15, 52, 203, 877,  . . . ),  provide answers to a variety of mathematical counting-problems, including counting the number of rhyme schemes for stanzas of poetry.  In English, earliest classification of rhyme schemes dates back to George Puttenham and his treatise, The Arte of English Poesie (published around 1590).