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 A386246 #7 Jul 20 2025 15:31:39 %S A386246 27,108,171,240,456,603,744,936,988,1424,1702,1737,1820,1899,1904, %T A386246 1989,2166,2261,2366,2817,2873,3283,3553,3681,3728,3784,3852,3894, %U A386246 4266,4437,4700,4923,4975,5005,5008,5073,5117,5193,5278,5356,5418,5820,6050,6486,6576,6627,6651,6775,7947,8250,9116 %N A386246 Composite numbers k such that A075254(k) is a square. %C A386246 Composite numbers k such that k + sopfr(k) is a square, where sopfr(k) is the sum of prime factors of k with multiplicity. %C A386246 Contains no semiprimes. %C A386246 Includes 9*p if p is a prime of the form (x^2-6)/10 where x == 4 or 6 (mod 10). %C A386246 Is this sequence disjoint from A386245? %H A386246 Robert Israel, <a href="/A386246/b386246.txt">Table of n, a(n) for n = 1..10000</a> %e A386246 a(3) = 171 is a term because 171 = 3^2 * 19 is composite and 171 + 3 + 3 + 19 = 196 = 14^2 is a square. %p A386246 filter:= proc(n) local t; %p A386246 if isprime(n) then return false fi; %p A386246 issqr(n + add(t[1]*t[2], t=ifactors(n)[2])) %p A386246 end proc: %p A386246 select(filter, [$4..10000]); %Y A386246 Cf. A075254, A386245. %K A386246 nonn %O A386246 1,1 %A A386246 _Will Gosnell_ and _Robert Israel_, Jul 16 2025