OFFSET
1,2
FORMULA
EXAMPLE
The a(2) = 1 + 9 = 10:
({1,2}) ({},{1,2})
({1},{2})
({1},{1,2})
({2},{1,2})
({2},{1})
({1,2},{})
({1,2},{1})
({1,2},{2})
({1,2},{1,2}).
MATHEMATICA
a[n_] := a[n] = Sum[(2^k - 1)^n, {k, 1, n}]; Table[a[n], {n, 1, 15}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Rajesh Kumar Mohapatra and Ranjan Kumar Dhani, Jan 21 2026
STATUS
approved
