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A277971 a(1) = 1; a(n) > a(n-1) is the smallest number whose name in English contains the first letter of the name of a(n-1). 5

%I

%S 1,2,3,8,9,10,12,13,14,15,24,25,26,27,28,29,30,31,32,33,34,35,36,37,

%T 38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,64,

%U 65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,86,87,88,89,90,91

%N a(1) = 1; a(n) > a(n-1) is the smallest number whose name in English contains the first letter of the name of a(n-1).

%t names={"one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen","twenty"};

%t lst={1};next[n_]:=next[n]=Module[{pos=Last[lst]+1},

%t While[StringPosition[names[[pos]],First[Characters[names[[Last[lst]]]]]]=={}&&pos<=Length[names],pos++];

%t AppendTo[lst,pos]]; seq[n_]:=Nest[next,1,n];seq[9]

%Y Cf. A277972.

%K easy,nonn,word

%O 1,2

%A _Ivan N. Ianakiev_, Nov 07 2016

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Last modified October 20 22:00 EDT 2021. Contains 348119 sequences. (Running on oeis4.)