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a(n) = Sum_{ k <= n, k is not an i-th power with i >= 2} k.
2

%I #8 Sep 08 2024 19:56:04

%S 1,3,6,6,11,17,24,24,24,34,45,57,70,84,99,99,116,134,153,173,194,216,

%T 239,263,263,289,289,317,346,376,407,407,440,474,509,509,546,584,623,

%U 663,704,746,789,833,878,924,971,1019,1019,1069,1120,1172,1225,1279

%N a(n) = Sum_{ k <= n, k is not an i-th power with i >= 2} k.

%o (PARI) a(n) = sum(x=1, n, if(!ispower(x), x));

%K nonn

%O 1,2

%A _Cino Hilliard_, Nov 07 2007