A362121 a(n) is the smallest nonnegative number whose British English name has the letter "e" in the n-th position.

8, 0, 1, 3, 3, 12, 13, 17, 21, 23, 23, 73, 1700, 108, 107, 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, 101123, 101173

Offset

1,1

References

GCHQ, The GCHQ Puzzle Book, Penguin, 2016. See page 70.

Links

Table of n, a(n) for n=1..49.

Prog

(Python)
from num2words import num2words
from itertools import count, islice
def n2w(n):
    return "".join(c for c in num2words(n, lang='en_GB') if c.isalpha())
def A362121(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([A362121(n) for n in range(1, 31)]) # Michael S. Branicky, Apr 21 2023
(Python) # faster for initial segment of sequence; uses n2w, imports above
def A362121gen(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(A362121gen(), 50))) # Michael S. Branicky, Apr 21 2023

Crossrefs

See A164790, A362120, and A362122 for other versions.

Sequence in context: A329074 A296434 A164790 * A250219 A037448 A011470

Adjacent sequences: A362118 A362119 A362120 * A362122 A362123 A362124

Keyword

nonn,word

Author

N. J. A. Sloane, Apr 20 2023

Extensions

a(14) and beyond from Michael S. Branicky, Apr 21 2023

Status

approved