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 A070810 #17 Nov 08 2024 07:19:55
%S A070810 4,6,8,9,10,12,14,16,18,20,22,24,25,28,32,36,38,39,40,42,44,46,48,50,
%T A070810 55,56,58,62,64,65,72,76,77,80,84,88,92,94,96,100,112,116,118,124,128,
%U A070810 134,144,152,158,160,165,168,176,184,188,192,200,202,224,232,235,236
%N A070810 Nonprime numbers k such that phi(k-phi(k)) = A054571(k) is a power of 2.
%H A070810 Amiram Eldar, <a href="/A070810/b070810.txt">Table of n, a(n) for n = 1..6018</a> (terms below 10^10)
%e A070810 For k = 168: 168 - phi(168) = 168-48 = 120, phi(120) = 32, a power of 2.
%t A070810 Do[s=EulerPhi[n-EulerPhi[n]]; If[IntegerQ[Log[2, s]]&&!PrimeQ[n], Print[n]], {n, 1, 256}]
%o A070810 (PARI) is(k) = if(k == 1 || isprime(k), 0, my(m = eulerphi(k - eulerphi(k))); m >> valuation(m, 2) == 1); \\ _Amiram Eldar_, Nov 08 2024
%Y A070810 Cf. A000010, A054571, A051953, A070556, A070806, A070807, A070809, A070811, A070812.
%K A070810 nonn
%O A070810 1,1
%A A070810 _Labos Elemer_, May 08 2002