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

%I A362121 #11 Apr 21 2023 11:37:54
%S A362121 8,0,1,3,3,12,13,17,21,23,23,73,1700,108,107,101,103,103,112,113,117,
%T A362121 121,123,123,173,323,373,1103,1103,1112,1113,1117,1121,1123,1123,1173,
%U A362121 1323,1373,3323,3373,11373,13323,13373,17373,23323,23373,73373,101123,101173
%N A362121 a(n) is the smallest nonnegative number whose British English name has the letter "e" in the n-th position.
%D A362121 GCHQ, The GCHQ Puzzle Book, Penguin, 2016. See page 70.
%o A362121 (Python)
%o A362121 from num2words import num2words
%o A362121 from itertools import count, islice
%o A362121 def n2w(n):
%o A362121     return "".join(c for c in num2words(n, lang='en_GB') if c.isalpha())
%o A362121 def A362121(n, t="e", i0=0): # t is target letter, i0 is start
%o A362121     return next(i for i in count(i0) if len(w:=n2w(i))>=n and w[n-1]==t)
%o A362121 print([A362121(n) for n in range(1, 31)]) # _Michael S. Branicky_, Apr 21 2023
%o A362121 (Python) # faster for initial segment of sequence; uses n2w, imports above
%o A362121 def A362121gen(t="e", i0=0, offset=1): # generator of terms w
%o A362121     adict, n = dict(), offset
%o A362121     for i in count(i0):
%o A362121         w = n2w(i)
%o A362121         if t in w:
%o A362121             locs = [i+1 for i, c in enumerate(w) if w[i] == t]
%o A362121             for v in locs:
%o A362121                 if v not in adict: adict[v] = i
%o A362121         while n in adict: yield adict[n]; n += 1
%o A362121 print(list(islice(A362121gen(), 50))) # _Michael S. Branicky_, Apr 21 2023
%Y A362121 See A164790, A362120, and A362122 for other versions.
%K A362121 nonn,word
%O A362121 1,1
%A A362121 _N. J. A. Sloane_, Apr 20 2023
%E A362121 a(14) and beyond from _Michael S. Branicky_, Apr 21 2023