Let us define P(N) as the Nth Pentagonal number and H(N) as the Nth Hexagonal number.
All the positive pentagonal numbers and hexagonal numbers are now considered alternately in order, that is:
P(1), H(2), P(3), H(4), P(5), H(6),.....
Writing these without commas or spaces results in this infinite string:

             161228356670120117190......

Determine the 2022th digit in the above pattern. What is the 20220th digit in the above pattern?

*** P(N)= N(3N-1)/2, and, H(N) = N(2N-1), so that:
P(1)=1, H(2)= 6, P(3)= 12, H(4) = 28, P(5) = 35, H(6) = 66, ..... and so on

Posted by K Sengupta on 2022-05-02 23:50:28