OFFSET
1,2
COMMENTS
For any pair of contiguous terms, one of the terms uses fewer digits than the other. This term is called the mask. Put the mask on the other term, starting from the left. What is not covered by the mask rebuilds, term by term, the starting sequence.
The n-th term of the sequence has exactly 2^(n-1) digits, which means that a(21) has more than one million digits.
The sequence starts with a(1) = 1, then a(n) = 10^(2^(n-1)-1)+a(n-1).
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..11
EXAMPLE
In the pair (1,11), 1 is the mask; 1 emerges = a(1);
In the pair (11,1011), 11 is the mask; 11 emerges = a(2);
In the pair (1011,10001011), 1011 is the mask; 1011 emerges = a(3); etc.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Apr 30 2018
STATUS
approved