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 A244520 #18 Dec 27 2017 03:11:05 %S A244520 1,3,5,11,15,21,29,35,39,41,51,65,95,105,155,165,179,191,221,231,239, %T A244520 281,329,371,419,431,485,519,611,641,659,809,905,935,989,1019,1031, %U A244520 1049,1121,1199,1229,1289,1451,1469,1481,1509,1541,1661,1821,1931,2109,2129,2141,2339,2549,2795,2969,3021,3039,3189,3299,3329 %N A244520 a(n) = A080715(n+1) / 2. %C A244520 Numbers k such that 2d + k/d is prime for every d|k. Such k must be an odd squarefree number. Primes in the sequence are A045536. - _Thomas Ordowski_, Nov 16 2017 %H A244520 Alois P. Heinz, <a href="/A244520/b244520.txt">Table of n, a(n) for n = 1..1000</a> %F A244520 A088627(a(n)) = A000005(a(n)) = 2^m. - _Thomas Ordowski_, Nov 16 2017 %t A244520 Select[Range[1, 3400, 2], Function[n, AllTrue[Divisors@ n, PrimeQ[2 # + n/#] &]]] (* _Michael De Vlieger_, Nov 18 2017 *) %o A244520 (PARI) is_ok(n)=n=2*n;fordiv(n,d,if(!isprime(d+n/d),return(0)));return(1); %o A244520 for(n=1,10^4,if(is_ok(n),print1(n,", "))); %Y A244520 Cf. A045536, A080715, A088627. %K A244520 nonn %O A244520 1,2 %A A244520 _Joerg Arndt_, Jul 10 2014