A333293 a(n) = Sum_{k=1..n-1} k^2*phi(k) + n^2*phi(n)/2, where phi = A000010.

3, 14, 39, 105, 191, 374, 649, 1020, 1463, 2268, 3161, 4463, 6065, 7553, 9477, 12813, 16097, 20318, 25167, 29413, 34479, 42718, 50841, 59395, 69701, 80318, 91583, 108061, 123435, 141450, 164057, 183139, 203277, 227225, 249701, 282119, 319757, 351005, 382057, 428477, 472681, 522094, 580283, 623943, 671519

Offset: 2

Author

N. J. A. Sloane, Mar 23 2020

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 2..10000

Crossrefs

Cf. A319087, A000010.

Next-to-last diagonal of A333292.

Programs

Maple

P:= [seq(k^2*numtheory:-phi(k),k=1..100)]:
T:= ListTools:-PartialSums(P):
seq(T[i-1]+P[i]/2,i=2..100); # Robert Israel, Mar 24 2020

PARI

a(n) = sum(k=1, n-1, k^2*eulerphi(k)) + n^2*eulerphi(n)/2; \\ Michel Marcus, Mar 23 2020