A309350 - OEIS

%I #9 Apr 20 2020 19:11:04

%S 2,3,10,17,36,60,84,88,96,104,108,120,132,136,144,152,156,168,180,184,

%T 192,204,208,216,228,232,240,248,252,264,276,288,296,300,312,324,328,

%U 336,344,348,352,360,372,376,384,392,396,400,408,420,424,444,450,456

%N Sums of two refactorable numbers whose product and difference are also refactorable.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RefactorableNumber.html">Refactorable Number</a>

%t Flatten[Table[If[Sum[ (1 - Ceiling[(n - 2 i)/DivisorSigma[0, n - 2 i]] + Floor[(n - 2 i)/DivisorSigma[0, n - 2 i]]) (1 - Ceiling[(i (n - i))/DivisorSigma[0, i (n - i)]] + Floor[(i (n - i))/DivisorSigma[0, i (n - i)]]) (1 - Ceiling[i/DivisorSigma[0, i]] + Floor[i/DivisorSigma[0, i]]) (1 - Ceiling[(n - i)/DivisorSigma[0, n - i]] + Floor[(n - i)/DivisorSigma[0, n - i]]), {i, Floor[n/2]}] > 0, n, {}], {n, 500}]]

%Y Cf. A033950.

%K nonn

%O 1,1

%A _Wesley Ivan Hurt_, Jul 24 2019