81380

Appears in sequences

• Base-5 digits are, in order, the first n terms of the periodic sequence with initial period 1,0.at n=7A033115
• Numbers whose base-5 representation has exactly 8 runs.at n=0A043608
• a(n) = n*(n+1)*(8*n + 1)/6.at n=39A132124
• a(n) is the number of ways to split [n] = {1,2,...,n} into two (possibly empty) complementary intervals {1,2,...,i} and {i+1,i+2,...,n} and then, if both intervals are nonempty, select 2 nonempty blocks/cells (i.e., subintervals) from each of them, or if one of the intervals is empty, select 2 nonempty blocks/cells from the nonempty interval.at n=25A353232