OFFSET
1,2
LINKS
Carlos Eduardo Olivieri, A polynomial from divisors of n
EXAMPLE
For n = 4: a(4) = 4^1 + 2^2 + 1^3 = 9.
For n = 5: a(5) = 5^1 + 1^2 = 6.
For n = 6: a(6) = 6^1 + 3^2 + 2^3 + 1^4 = 24.
MATHEMATICA
a[n_] := Sum[Sort[Divisors[n], #1 > #2 &][[i]]^i, {i, DivisorSigma[0, n]}]; Table[a[n], {n, 60}]
PROG
(PARI) a(n) = my(d = divisors(n)); sum(k=1, #d, d[k]^(#d-k+1)); \\ Michel Marcus, Jan 01 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Carlos Eduardo Olivieri, Nov 29 2015
STATUS
approved