1st: 1*5^0 + 0 = 1

2nd: 1*5^1 – 1 = 4, 1*5^1 + 0 = 5, 1*5^1 + 1 = 6
3rd: 2*5^1 – 1 = 9

4th: 1*5^2 – 1 = 24, 1*5^2 + 0 = 25
5th: 2*5^2 – 1 = 49, 2*5^2 + 1 = 51
6th: 3*5^2 + 0 = 75,3*5^2 + 1 = 76
7th: 4*5^2 – 1 = 99

8th: 1*5^3 + 0 = 125
9th: 2*5^3 – 1 = 249, 2*5^3 + 1 = 251
10th: 3*5^3 + 0 = 375, 3*5^3 + 1 = 376
11th: 4*5^3 – 1 = 499, 4*5^3 + 1 = 501
12th: 5*5^3 – 1 = 624,5*5^3 + 0 = 625
13th: 6*5^3 – 1 = 749,6*5^3 + 1 = 751
14th: 7*5^3 + 0 = 875
15th: 8*5^3 – 1 = 999

center(t) = (t – 2^F + 1)*5^F
F = Floor[Log[t]/Log[2]]
t = batch