# Contents

## Idea

A generalization of the notion of homotopy groups.

## Definition

Given a pointed space $X$ and finitely generated abelian group $A$ and $n\ge2$, we set

$\pi_n(X,A) \;\coloneqq\; [P^n(A),X] \,,$

where $P^n(A)$ is the $n$th Peterson space of $A$ and $[-,-]$ denotes pointed homotopy classes.