a(n) = Sum_{1 <= x_1, x_2, x_3, x_4 <= n} sigma( ( n/gcd(x_1, x_2, x_3, x_4, n) )^4 ).
A373135
a(n) = Sum_{1 <= x_1, x_2, x_3, x_4 <= n} sigma( ( n/gcd(x_1, x_2, x_3, x_4, n) )^4 ).
Terms
- a(0) =1a(1) =466a(2) =9681a(3) =123106a(4) =487345a(5) =4511346a(6) =6722401a(7) =31576546a(8) =63779361a(9) =227102770a(10) =235777201a(11) =1191789186a(12) =883674961a(13) =3132638866a(14) =4717986945a(15) =8084578786a(16) =7411648321a(17) =29721182226a(18) =17926949521a(19) =59995093570a(20) =65079564081a(21) =109872175666a(22) =81870270241a(23) =305692541826
External references
- oeis: A373135