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

Author

Eric Angelini, Oct 27 2004

Keywords

• base
• easy
• nonn

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

Examples

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

Links

• Index to the OEIS: Entries related to self-referencing sequences.

Crossrefs

Cf. A114134, A098645, A210414-A210423.

Programs

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

Extensions

Edited and extended by Max Alekseyev, Feb 06 2010