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 A274771 #15 Sep 08 2022 08:46:17
%S A274771 0,0,1,1,2,1,3,1,3,2,4,1,5,3,2,2,6,3,7,2,3,4,8,1,8,5,7,3,9,2,10,4,4,6,
%T A274771 5,3,11,7,5,2,12,3,13,4,5,8,14,2,13,8,6,5,15,7,8,3,7,9,16,2,17,10,3,6,
%U A274771 5,4,18,6,8,5,19,3,20,11,8,7,10,5,21,2
%N A274771 Number of primes <= n-th Carmichael lambda number.
%F A274771 a(n) = A000720(A002322(n)). - _Michel Marcus_, Nov 11 2016
%p A274771 with(numtheory):
%p A274771 a:= n-> pi(lambda(n)):
%p A274771 seq(a(n), n=1..100); # _Alois P. Heinz_, Nov 11 2016
%t A274771 Table[PrimePi[CarmichaelLambda[n]], {n, 100}]
%o A274771 (Magma) [0] cat [#PrimesUpTo(CarmichaelLambda(n)): n in [2..100]];
%Y A274771 Cf. A002322, A054782, A070804, A273974, A277062, A277063.
%K A274771 nonn
%O A274771 1,5
%A A274771 _Vincenzo Librandi_, Nov 11 2016