A173206 a(n) = Smallest number which has in its English name the letter "T" in the n-th position beginning the count from the end.

8, 20, 2, 13, 3, 12, 23, 13, 21, 24, 23, 300, 201, 204, 203, 211, 215, 213, 217, 224, 223, 273, 323, 373, 1115, 1113, 1117, 1124, 1123, 1173, 1323, 1373, 2173, 2323, 2373, 3323, 3373, 12373, 13323, 13373, 21373, 23323, 23373, 201323, 201373, 203323, 203373

Offset

1,1

Comments

American spelling is used, all spaces and hyphens are ignored. - Sean A. Irvine, Jan 28 2026

Links

Table of n, a(n) for n=1..47.

Example

a(1) = eighT, a(2) = twenTy, a(3) = Two, a(4) = thirTeen, a(5) = Three, etc.

Prog

(Python)
from num2words import num2words
from itertools import count, islice
def n2w(n): return "".join(c for c in num2words(n).replace(" and", "") if c.isalpha())
def agen(): # generator of terms
    n, adict = 1, dict()
    for k in count(0):
        s = n2w(k)
        tlocs = [len(s)-i for i in range(len(s)) if s[i]=='t']
        for v in tlocs:
            if v not in adict:
                adict[v] = k
                while n in adict: yield adict[n]; n += 1
print(list(islice(agen(), 43))) # Michael S. Branicky, Jan 28 2026

Crossrefs

Sequence in context: A282942 A225912 A120081 * A288423 A373743 A081963

Adjacent sequences: A173203 A173204 A173205 * A173207 A173208 A173209

Keyword

nonn,word

Author

Claudio Meller, Feb 12 2010

Extensions

More terms from Sean A. Irvine, Jan 28 2026

Status

approved