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.

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

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 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

Links

Table of n, a(n) for n=1..56.

Index to the OEIS: Entries related to self-referencing 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)); ); ) } \\ Max Alekseyev

Crossrefs

Cf. A114134, A098645, A210414-A210423.

Sequence in context: A219331 A229862 A302599 * A343570 A320021 A081407

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