OFFSET
1,2
COMMENTS
a(p-1) is divisible by p^3 for prime p>3. a(p^2-1) is divisible by p^6 for prime p>3. a(p^3-1) is divisible by p^9 for prime p>3.
FORMULA
a(n) = numerator(Sum_{i=1..n} i^n/(n+1-i)).
EXAMPLE
a(1) = numerator(1/1) = 1.
a(2) = numerator(1/2 + 4/1) = 9.
a(3) = numerator(1/3 + 8/2 + 27/1) = 94.
a(4) = numerator(1/4 + 16/3 + 81/2 + 256/1) = 3625.
MATHEMATICA
Table[Numerator[Sum[i^n/(n+1-i), {i, 1, n}]], {n, 1, 20}]
CROSSREFS
KEYWORD
frac,nonn,easy
AUTHOR
Alexander Adamchuk, Jun 17 2006
STATUS
approved