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 A074810 #19 Jan 29 2025 07:50:04 %S A074810 1,2,4,8,9,28,65,114,174,186,246,623,1784,1832,1912,5121,13810,14090, %T A074810 39413,40403,808822,809858,810026,2201505,2202735,6047408,6048656, %U A074810 16463939,16467271,16472371,121482371,121495747,330358060,898100679 %N A074810 Numbers k such that the number of primes between k and 2k (inclusive) = largest prime factor of k. %e A074810 28 is a term because there are 7 primes between n = 28 and 2n = 56: 29, 31, 37, 41, 43, 47, 53; and the largest prime dividing 28 is 7. %p A074810 with(numtheory): a:=proc(n) if pi(2*n)-pi(n-1)=max(1, factorset(n)) then n fi end: seq(a(n), n=1..1000); # _Emeric Deutsch_, Feb 05 2006 %Y A074810 Cf. A006530, A035250. %K A074810 nonn %O A074810 1,2 %A A074810 _Jason Earls_, Sep 08 2002 %E A074810 More terms from _Emeric Deutsch_, Feb 05 2006 %E A074810 a(24)-a(34) from _Donovan Johnson_, Apr 23 2010