A331882 a(n) is the number of digits in the decimal expansion of the fractional part of Pi needed to contain n occurrences of an n-digit substring.

1, 22, 219, 1805, 25499, 168882, 3566679, 29325629

Offset: 1

Author

Stijn Dierckx, Jan 30 2020

Keywords

• nonn
• base
• hard
• more

Examples

			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

Cf. A000796, A159345, A331881 (the repeated n-digit substrings).