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 A330702 #13 Jun 13 2020 03:23:31 %S A330702 70,308,572,2132,4292,6764,12212,32804,72836,79292,169724,198596, %T A330702 207692,289052,362972,392426,545876,547724,611612,651932,678812, %U A330702 687812,809252,842012,868436,930932,1030772,1032956,1122932,1336052,1627772,1705892,1722932,2173772 %N A330702 Numbers k such that psi(k) = psi(k + 2) and phi(k) = phi(k + 2), where psi(k) is the Dedekind psi function (A001615) and phi(k) is the Euler totient function (A000010). %C A330702 Sandor asked whether this sequence is infinite. %C A330702 Apparently the only common solution to psi(n) = psi(n+1) and phi(n) = phi(n+1) is 15. %H A330702 Amiram Eldar, <a href="/A330702/b330702.txt">Table of n, a(n) for n = 1..600</a> %H A330702 Jozsef Sandor, <a href="https://www.emis.de/journals/JIPAM/article546.html">On the composition of some arithmetic functions, II</a>, Journal of Inequalities in Pure and Applied Mathematics, Vol. 6, No. 3 (2005), Article 73. %e A330702 70 is a term since psi(70) = psi (72) = 144 and phi(70) = phi(72) = 24. %t A330702 psi[1] = 1; psi[n_] := n * Times @@ (1 + 1/Transpose[FactorInteger[n]][[1]]); Select[Range[10^5], psi[#] == psi[# + 2] && EulerPhi[#] == EulerPhi[#+2] &] %Y A330702 Intersection of A001494 and A330703. %Y A330702 Cf. A000010, A001615. %K A330702 nonn %O A330702 1,1 %A A330702 _Amiram Eldar_, Dec 26 2019