A282636 - OEIS

%I #7 Feb 23 2017 22:59:41

%S 1,2,8,9,10,28,38,88,89,91,97,107,122,132,142,152,162,172,182,192,202,

%T 208,228,238,248,258,268,278,288,298,308,328,338,348,358,368,378,388,

%U 398,808,809,812,821,823,825,829,831,833,835,839,841,843,845,849,851,853,855,859

%N a(1) = 1. a(n) is the smallest natural number such that a(n) > a(n-1), the name of a(n) in (American) English ends with the letter a(n-1) starts with, and a(n) makes the sequence extendable.

%C "a(n) makes the sequence extendable" means the name of a(n) does not start with any of the letters f and s.

%e 38 is followed by 88 as 48, 58, 68 and 78 cannot make the sequence extendable.

%t names = StringReplace[

%t    IntegerName /@ Range[1000], {"\[Hyphen]" -> "", " " -> ""}];

%t lst = {1}; next[n_] := next[n] =

%t   Module[{pos = Last[lst] + 1},

%t    While[

%t     Or[

%t      And[First[Characters[names[[Last[lst]]]]] !=

%t        Last[Characters[names[[pos]]]], pos <= Length[names]],

%t      MemberQ[{"f", "s"}, First[Characters[names[[pos]]]]] == True

%t      ],

%t     pos++

%t     ];

%t    AppendTo[lst, pos]

%t    ];

%t seq[n_] := Nest[next, 1, n]; seq[57]

%Y Cf. A277971, A277972, A281067, A281068, A282637.

%K easy,nonn,word

%O 1,2

%A _Ivan N. Ianakiev_, Feb 20 2017