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 A070002 #17 Mar 31 2021 02:34:53
%S A070002 45,90,135,175,180,270,350,360,405,525,540,700,720,810,875,1050,1080,
%T A070002 1215,1400,1440,1573,1575,1620,1750,2100,2160,2430,2625,2800,2880,
%U A070002 3146,3150,3240,3500,3645,4200,4320,4375,4719,4725,4860,5250,5491,5600,5760
%N A070002 Numbers k such that phi(P(k)) - P(phi(k)) = 1, where P(k) is the largest prime factor of k.
%C A070002 phi(P(k)) - P(phi(k)) = A000010(A006530(k)) - A006530(A000010(k)) = 1, where P(k) = largest prime factor of k. Value of commutator of phi and P functions at k equals 1.
%C A070002 Many but not all terms are divisible by 5.
%H A070002 Amiram Eldar, <a href="/A070002/b070002.txt">Table of n, a(n) for n = 1..10000</a>
%e A070002 m = 77077 = 7*7*11*11*13*13 is here because P(m) = 13, phi(P(13)) = 12, phi(m) = 55440 = 2*2*2*2*3*3*5*7*11 with P(Phi(55440)) = 13 and the difference is 13 - 12 = 1.
%t A070002 pf[n_] := FactorInteger[n][[-1, 1]];
%t A070002 Do[s=EulerPhi[pf[n]]-pf[EulerPhi[n]]; If[Equal[s, 1], Print[n]], {n, 3, 100000}]
%Y A070002 Cf. A000010, A006530, A068211, A070777, A070812, A070003, A070004, A007283, A070813, A070814, A070815, A070816.
%K A070002 nonn
%O A070002 1,1
%A A070002 _Labos Elemer_, May 07 2002