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 A250290 #30 May 13 2023 13:25:25 %S A250290 8,10,14,26,30,58,78 %N A250290 Numbers k such that Euler(k) (A122045(k)) is a semiprime. %C A250290 No more terms <= 200. %C A250290 k=7634 is a term, but it is not known to be the next term after 78. - _Jeppe Stig Nielsen_, May 12 2023 %H A250290 Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/matha1/matha133.htm">Euler numbers (n = 0 to 78)</a>. %H A250290 Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/matha1/matha1331.htm">Euler numbers (n = 80 to 106)</a>. %H A250290 Prime Pages, <a href="https://t5k.org/primes/page.php?id=136039">-E(7634)/1559</a>. %H A250290 Sam Wagstaff, <a href="http://homes.cerias.purdue.edu/~ssw/bernoulli/index.html">Factorization of Bernoulli and Euler numbers</a>. %e A250290 a(2) = 10 so Euler(10) = 50521 = 19 * 2659 is a semiprime. %o A250290 (PARI) is(k) = k%2==0 && bigomega(eulerfrac(k))==2 \\ slow, from _Jeppe Stig Nielsen_, May 12 2023 %Y A250290 Cf. A103234, A122045. %K A250290 nonn,more %O A250290 1,1 %A A250290 _Eric Chen_, Dec 24 2014