| <math>x, ~ {}^{\langle} x {}^{\rangle}, ~ {}^{\langle\langle} x {}^{\rangle\rangle}, ~ {}^{\langle\langle\langle} x {}^{\rangle\rangle\rangle}, ~ \ldots</math> | | <math>x, ~ {}^{\langle} x {}^{\rangle}, ~ {}^{\langle\langle} x {}^{\rangle\rangle}, ~ {}^{\langle\langle\langle} x {}^{\rangle\rangle\rangle}, ~ \ldots</math> |