A164790 a(n) is the smallest nonnegative number whose American English name has the letter "e" in the n-th position.
8, 0, 1, 3, 3, 12, 13, 17, 21, 23, 23, 73, 101, 103, 103, 112, 113, 117, 121, 123, 123, 173, 323, 373, 1103, 1103, 1112, 1113, 1117, 1121, 1123, 1123, 1173, 1323, 1373, 3323, 3373, 11373, 13323, 13373, 17373, 23323, 23373, 73373, 101373, 103323, 103373, 111373
Offset: 1
Examples
a(1)=8 ("Eight"), a(2)=0 ("zEro"), a(3)=1 ("onE"), a(4)=3 ("thrEe").
References
- GCHQ, The GCHQ Puzzle Book, Penguin, 2016. See page 70.
Crossrefs
Programs
-
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 A164790(n, t="e", i0=0): # t is target letter, i0 is start return next(i for i in count(i0) if len(w:=n2w(i))>=n and w[n-1]==t) print([A164790(n) for n in range(1, 38)]) # Michael S. Branicky, Apr 21 2023 -
Python
# faster for initial segment of sequence; uses n2w/imports above def A164790gen(t="e", i0=0, offset=1): # generator of terms w adict, n = dict(), offset for i in count(i0): w = n2w(i) if t in w: locs = [i+1 for i, c in enumerate(w) if w[i] == t] for v in locs: if v not in adict: adict[v] = i while n in adict: yield adict[n]; n += 1 print(list(islice(A164790gen(), 50))) # Michael S. Branicky, Apr 21 2023
Extensions
a(25) and beyond from Michael S. Branicky, Mar 25 2021
Name edited by N. J. A. Sloane, Apr 20 2023