A297792 a(n) = Sum_{d|n} min(d, n/d)^2.
1, 2, 2, 6, 2, 10, 2, 10, 11, 10, 2, 28, 2, 10, 20, 26, 2, 28, 2, 42, 20, 10, 2, 60, 27, 10, 20, 42, 2, 78, 2, 42, 20, 10, 52, 96, 2, 10, 20, 92, 2, 100, 2, 42, 70, 10, 2, 132, 51, 60, 20, 42, 2, 100, 52, 140, 20, 10, 2, 182, 2, 10, 118, 106, 52, 100, 2, 42, 20
Offset: 1
Keywords
Links
- Seiichi Manyama, Table of n, a(n) for n = 1..10000
Crossrefs
Programs
-
Mathematica
a[n_] := Block[{d = Divisors@n}, Plus @@ (Min[#, n/#]^2 & /@ d)]; Array[a, 70] (* Robert G. Wilson v, Jan 06 2018 *) -
PARI
{a(n) = sumdiv(n, d, min(d, n/d)^2)}
Formula
From Michel Marcus, Jan 09 2018: (Start)
a(p) = 2, for prime p.
a(2p) = 10, for odd prime p. (End)
a(r*p) = 2 + 2*r^2, where r, p are primes and p > r. - Bruno Berselli, Jan 09 2018
Comments