

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.


4



5, 6, 7, 8, 22, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270
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OFFSET

1,1


COMMENTS

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 222th 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


LINKS

Table of n, a(n) for n=1..56.
Index to the OEIS: Entries related to selfreferencing sequences.


EXAMPLE

The 5th digit of the sequence is a "2", the 6th digit also, then the 7th, the 8th, the 22nd etc.


PROG

(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)); ); ) } [From Max Alekseyev]


CROSSREFS

Cf. A114134, A098645, A210414A210423.
Sequence in context: A014097 A219331 A229862 * A081407 A205857 A196026
Adjacent sequences: A098667 A098668 A098669 * A098671 A098672 A098673


KEYWORD

base,easy,nonn


AUTHOR

Eric Angelini, Oct 27 2004


EXTENSIONS

Edited and extended by Max Alekseyev, Feb 06 2010


STATUS

approved



