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 A309835 #24 Dec 30 2023 12:35:14 %S A309835 5798663,5555564201311,5555574497311,5555593942711,66815976110703, %T A309835 69437045907973255623 %N A309835 Numbers k such that k + phi(k) is a repunit. %C A309835 Also in the sequence is 555555555555555555555556288388841217550575591423513701223. - _Robert Israel_, Aug 20 2019 %C A309835 The number 5975946235638859341313216528710061511 is also in the sequence. - _Daniel Suteu_, Aug 22 2019 %e A309835 5798663 is a terms since phi(5798663) = 5312448 and 5798663 + 5312448 = 11111111. %o A309835 (PARI) isok(k) = my(d=digits(k+eulerphi(k))); vecmin(d)==1 && vecmax(d)==1; \\ _Daniel Suteu_, Aug 22 2019 %Y A309835 Subsequence of A116018. %Y A309835 Cf. A000010, A002275, A121048, A244444. %K A309835 nonn,base,more %O A309835 1,1 %A A309835 _Giovanni Resta_, Aug 19 2019 %E A309835 a(5) from _Daniel Suteu_ confirmed by _Max Alekseyev_, Oct 25 2023 %E A309835 a(6) from _Max Alekseyev_, Nov 30 2023