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 A036553 #12 Jul 08 2025 21:45:03
%S A036553 -1,0,1,3,3,9,3,11,9,21,1,29,3,29,27,33,5,47,5,51,35,49,3,69,25,63,41,
%T A036553 69,1,93,13,77,65,85,59,113,5,101,77,119,5,143,9,121,107,119,11,169,
%U A036553 45,157,101,149,1,189,83,173,117,163,5,227,1,179,155
%N A036553 a(n) = phi(prime(n)) - prime(phi(n)).
%t A036553 Table[EulerPhi[Prime[n]]-Prime[EulerPhi[n]],{n,70}] (* _Harvey P. Dale_, May 16 2014 *)
%Y A036553 Cf. A000010, A000040, A048849.
%K A036553 sign,easy
%O A036553 1,4
%A A036553 _N. J. A. Sloane_