OFFSET
1,2
EXAMPLE
a(1) = 1, because we need 1 digit to have the first 1-digit substring ('1') appearing 1 time;
a(2) = 22, because we need 22 digits (1415926535897932384626) to have the first 2-digit substring ('26') appearing 2 times;
a(3) is 219, because we need 219 digits (1415....933446) to have the first 3-digit substring ('446') appearing 3 times;
and so on.
CROSSREFS
KEYWORD
nonn,base,hard,more
AUTHOR
Stijn Dierckx, Jan 30 2020
STATUS
approved