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A098670 Start with a(1) = 5. Construct slowest growing sequence such that the statement "the a(n)-th digit is a 2" is true for all n.

%I A098670 #16 Feb 02 2015 05:23:18
%S A098670 5,6,7,8,22,220,221,222,223,224,225,226,227,228,229,230,231,232,233,
%T A098670 234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,
%U A098670 251,252,253,254,255,256,257,258,259,260,261,262,263,264,265,266,267,268,269,270
%N A098670 Start with a(1) = 5. Construct slowest growing sequence such that the statement "the a(n)-th digit is a 2" is true for all n.
%C A098670 The sequence goes 5, 6, 7, 8, 22, 220, 221, ..., 290, 2222, 22222, 222222, ... for 275 more digits, then for most of the rest of the sequence, a(n+1)=a(n)+1. Starting with a(1)=3 yields 3, 4, 22, 23, ..., 30, 32, 222, 2222, 2223,... for at least 2000 more digits. (The 222nd digit happens to be the initial digit of a(63)=2271.) Starting with a(1)=4 yields 4, 5, 6, 22, 23, ..., 30, 222, 2222, 2223, ... See A210416 for a variant without requirement of growth. - _M. F. Hasler_, Oct 08 2013
%H A098670 <a href="/index/Se#self-referencing_sequences">Index to the OEIS: Entries related to self-referencing sequences</a>.
%e A098670 The 5th digit of the sequence is a "2", the 6th digit also, then the 7th, the 8th, the 22nd etc.
%o A098670 (PARI) { a=5; P=Set(); L=0; while(1, print1(a,", "); P=setunion(P,Set([a])); L+=#Str(a); until(g, g=1; a++; s=Vec(Str(a)); for(i=1,#s, if(setsearch(P,L+i)&&s[i]!="2",g=0;break)); ); ) } \\ _Max Alekseyev_
%Y A098670 Cf. A114134, A098645, A210414-A210423.
%K A098670 base,easy,nonn
%O A098670 1,1
%A A098670 _Eric Angelini_, Oct 27 2004
%E A098670 Edited and extended by _Max Alekseyev_, Feb 06 2010