A344134 - OEIS

%I #18 May 12 2021 10:15:43

%S 1,15,22,91,36,330,50,387,193,540,78,2002,92,750,792,1363,120,2895,

%T 134,3276,1100,1170,162,8514,511,1380,1192,4550,204,11880,218,4275,

%U 1716,1800,1800,17563,260,2010,2024,13932,288,16500,302,7098,6948,2430,330,29986,981,7665,2640,8372,372,17880

%N a(n) = Sum_{i|n, j|n, k|n} lcm(i,j,k).

%F a(n) = Sum_{i|n, j|n, k|n} n/gcd(i,j,k).

%F If p is prime, a(p) = 1 + 7*p.

%t a[n_]:= Sum[n/GCD[i,j,k], {i, (d = Divisors[n])}, {j, d}, {k, d}]; Array[a, 50] (* _Amiram Eldar_, May 10 2021 *)

%o (PARI) a(n) = sumdiv(n, i, sumdiv(n, j, sumdiv(n, k, lcm([i, j, k]))));

%o (PARI) a(n) = sumdiv(n, i, sumdiv(n, j, sumdiv(n, k, n/gcd([i, j, k]))));

%Y Cf. A064950, A344132, A344133, A344135.

%K nonn,mult

%O 1,2

%A _Seiichi Manyama_, May 10 2021