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A173203 a(n) is the smallest number which has in its English name the letter "e" in the n-th position beginning the count from the end, or -1 if no such number exists.

%I A173203 #17 Mar 09 2022 01:13:58
%S A173203 1,3,13,7,8,11,21,17,23,74,73,104,103,111,115,113,117,124,123,173,373,
%T A173203 723,773,873,1103,1111,1115,1113,1117,1124,1123,1173,1323,1373,3373,
%U A173203 7323,7373,8373,11373,17323,17373,23373,73323,73373,103323,103373,111373
%N A173203 a(n) is the smallest number which has in its English name the letter "e" in the n-th position beginning the count from the end, or -1 if no such number exists.
%H A173203 Robert P. P. McKone, <a href="/A173203/b173203.txt">Table of n, a(n) for n = 1..58</a>
%e A173203 a(1) = onE, a(2) = thrEe, a(3) =thirtEen, a(4) = sEven, a(5) = Eight, a(6) = Eleven, etc.
%t A173203 ePos[n_] := Flatten@Position[DeleteCases[Reverse@Characters@IntegerName[n, "Words"], a_ /; MemberQ[{" ", "\[Hyphen]"}, a]], "e"]; t = {}; i = 1; Monitor[Table[Do[If[MemberQ[ePos[i], n], Return[lst = AppendTo[t, i]; i = 1; lst], i++], \[Infinity]], {n, 1, 47, 1}] // Last, {ProgressIndicator[n, {1, 47}], n, i}] (* _Robert P. P. McKone_, Feb 07 2022 *)
%Y A173203 Cf. A164790 ("e" in n-th position).
%Y A173203 Cf. A173204 (similar for "n"), A173206 (similar for "t").
%K A173203 nonn,word
%O A173203 1,2
%A A173203 _Claudio Meller_, Feb 12 2010
%E A173203 More terms from _Robert P. P. McKone_, Feb 08 2022