1,7

V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

a(n) = A007147(n) - [n^2/12] - 1.

A016116 := n->2^floor(n/2):with(numtheory): A000016 := proc(n) local d, t1: if n = 0 then RETURN(1) else t1 := 0; for d from 1 to n do if n mod d = 0 and d mod 2 = 1 then t1 := t1+phi(d)*2^(n/ d)/(2*n); fi; od; RETURN(t1); fi; end: A007147 := n->1/2*(A016116(n-1)+A000016(n)): A059736 := n->A007147(n) - floor(n^2/12) - 1: for j from 1 to 100 do printf(`%d, `, A059736(j)) od:

a[n_] := (1/2)*(2^Quotient[n - 1, 2] + Total[(Mod[#, 2]*EulerPhi[#]*2^(n/#) &) /@ Divisors[n]]/(2*n)) - Floor[n^2/12] - 1;

Array[a, 36] (* Jean-François Alcover, Aug 30 2019 *)

Sequence in context: A321411 A242251 A122537 * A261682 A102731 A007179

Adjacent sequences: A059733 A059734 A059735 * A059737 A059738 A059739

nonn,easy

N. J. A. Sloane, Feb 09 2001

More terms from James Sellers, Feb 20 2001

approved