This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A247087 #26 Sep 03 2024 08:25:32
%S A247087 0,1,3,4,9,25,41,39,168,462,442,1939,2571,3998,5123,17040,24853,38887,
%T A247087 195022,183430,404386,381060,1162366,2105509,1799881,5966593,5380661,
%U A247087 14184985,10473967,22631261,135452589,109540327,244730051,487610708,604467085,671043205,3350187738
%N A247087 a(n) = pi(phi(p(P(n)))) = A000720(A000010(A000041(A000040(n)))).
%H A247087 Amiram Eldar, <a href="/A247087/b247087.txt">Table of n, a(n) for n = 1..90</a> (calculated using Kim Walisch's primecount)
%H A247087 Kim Walisch, <a href="https://github.com/kimwalisch/primecount">Fast C++ prime counting function implementation (primecount)</a>.
%F A247087 a(n) = A070804(A058698(n)) = A000720(A000010(A000041(A000040(n)))).
%p A247087 with(numtheory): with(combinat): p:=numbpart: P:=ithprime:
%p A247087 a:= n-> pi(phi(p(P(n)))):
%p A247087 seq(a(n), n=1..20);
%t A247087 a[n_] := PrimePi @ EulerPhi @ PartitionsP @ Prime @ n;
%t A247087 Table[a[n], {n, 1, 30}] (* _Jean-François Alcover_, Mar 25 2017 *)
%Y A247087 Cf. A000010, A000040, A000041, A000720, A058697, A058698, A070804.
%K A247087 nonn
%O A247087 1,3
%A A247087 _Alois P. Heinz_, Mar 14 2015
%E A247087 a(31)-a(37) from _Amiram Eldar_, Sep 03 2024