In his poem “He Revisits His First School” and in his autobiography Hardy describes himself as seeing a “certain poetry” in the schoolboy maths he learnt from Francis Walkingame’s Tutor’s Assistant and other primers. This essay takes that claim seriously, investigating that mathematics in its mid-century context, and exploring mathematical structures implicit in his poetry and prose. In particular it examines the relation between love and narrative solutions to love-triangles, and between the mathematics of series (describable in terms of what mathematicians call ordinality) and sets (describable in terms of cardinality) as they relate to human experience. Alain Badiou’s work on mathematics offers one way of talking about Hardy’s tendency to move from the sometimes fixated seriality of love (as in The Well-Beloved) to a more open stance that might embrace the multiplicity of the world.