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 A172042 #12 Apr 09 2021 03:51:10
%S A172042 1,4,8,16,32,64,96,120,240,192,288,384,384,528,1056,1344,896,960,960,
%T A172042 1152,1728,1920,3200,2560,2560,2560,3328,3744,3456,4032,3456,6144,
%U A172042 5632,6336,5760,5760,7776,8856,13776,14784,8448,8640,9216,10752,10080,8640
%N A172042 a(n) = A000010(A083553(n)).
%C A172042 Except for the first term, a(n) is divisible by 4.
%H A172042 Amiram Eldar, <a href="/A172042/b172042.txt">Table of n, a(n) for n = 1..10000</a>
%p A172042 A083553 := proc(n) (ithprime(n+1)-1)*(ithprime(n)-1) ; end proc: A172042 := proc(n) numtheory[phi](A083553(n)) ; end proc: seq(A172042(n),n=1..80) ; # _R. J. Mathar_, Jan 30 2010
%t A172042 Table[EulerPhi[(Prime[n + 1] - 1)*(Prime[n] - 1)], {n, 1, 50}] (* _Amiram Eldar_, Apr 09 2021 *)
%o A172042 (PARI) a(n)=my(p=prime(n));eulerphi((p-1)*(nextprime(p+1)-1)) \\ _Charles R Greathouse IV_, Mar 05 2013
%Y A172042 Cf. A000010, A083553.
%K A172042 easy,nonn
%O A172042 1,2
%A A172042 _Giovanni Teofilatto_, Jan 24 2010
%E A172042 a(2) inserted and terms beyond a(10) added by _R. J. Mathar_, Jan 30 2010