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a(n) = A007821(n) - A022449(n).
2

%I #9 Jul 31 2017 03:33:06

%S 1,5,9,9,9,15,16,17,18,17,25,19,21,27,31,26,21,22,21,35,38,31,35,31,

%T 34,33,37,39,49,49,33,52,49,47,39,43,47,47,48,48,41,49,48,60,59,59,49,

%U 52,58,58,63,71,75,65,65,67,71,79,75,81,84,77,65,69,72,72,67,69,61,65,65

%N a(n) = A007821(n) - A022449(n).

%C Values of commutator of A000040 and A002808 functions i.e., of prime() and composite().

%t c[n_Integer] := FixedPoint[n+PrimePi[ # ]+1&, n] Table[Prime[c[w]]-c[Prime[w]], {w, 1, 10000}];

%Y Cf. A000040, A002808, A007821, A022449.

%K nonn

%O 1,2

%A _Labos Elemer_, Jul 19 2002