The sequence is finite as long as there are stable principles in the procedure for naming numbers in English.
Table of n, a(n) for n=1..19.
Wikipedia, Names of large numbers
Robert G. Wilson v, English names for the numbers from 0 to 11159 without spaces or hyphens
Index entries for sequences related to names of numbers
A159451(a(n)) = 0.
Sequence in context: A330513 A246092 A017906 * A044963 A044825 A048311
Adjacent sequences: A159449 A159450 A159451 * A159453 A159454 A159455
Reinhard Zumkeller, Apr 12 2009