%I #26 Sep 03 2024 08:25:32

%S 0,1,3,4,9,25,41,39,168,462,442,1939,2571,3998,5123,17040,24853,38887,

%T 195022,183430,404386,381060,1162366,2105509,1799881,5966593,5380661,

%U 14184985,10473967,22631261,135452589,109540327,244730051,487610708,604467085,671043205,3350187738

%N a(n) = pi(phi(p(P(n)))) = A000720(A000010(A000041(A000040(n)))).

%H Amiram Eldar, <a href="/A247087/b247087.txt">Table of n, a(n) for n = 1..90</a> (calculated using Kim Walisch's primecount)

%H Kim Walisch, <a href="https://github.com/kimwalisch/primecount">Fast C++ prime counting function implementation (primecount)</a>.

%F a(n) = A070804(A058698(n)) = A000720(A000010(A000041(A000040(n)))).

%p with(numtheory): with(combinat): p:=numbpart: P:=ithprime:

%p a:= n-> pi(phi(p(P(n)))):

%p seq(a(n), n=1..20);

%t a[n_] := PrimePi @ EulerPhi @ PartitionsP @ Prime @ n;

%t Table[a[n], {n, 1, 30}] (* _Jean-François Alcover_, Mar 25 2017 *)

%Y Cf. A000010, A000040, A000041, A000720, A058697, A058698, A070804.

%K nonn

%O 1,3

%A _Alois P. Heinz_, Mar 14 2015

%E a(31)-a(37) from _Amiram Eldar_, Sep 03 2024