A309350 Sums of two refactorable numbers whose product and difference are also refactorable.

2, 3, 10, 17, 36, 60, 84, 88, 96, 104, 108, 120, 132, 136, 144, 152, 156, 168, 180, 184, 192, 204, 208, 216, 228, 232, 240, 248, 252, 264, 276, 288, 296, 300, 312, 324, 328, 336, 344, 348, 352, 360, 372, 376, 384, 392, 396, 400, 408, 420, 424, 444, 450, 456

Offset

1,1

Links

Table of n, a(n) for n=1..54.

Eric Weisstein's World of Mathematics, Refactorable Number

Mathematica

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}]]

Crossrefs

Cf. A033950.

Sequence in context: A060744 A213391 A328343 * A300285 A192798 A143609

Adjacent sequences: A309347 A309348 A309349 * A309351 A309352 A309353

Keyword

nonn

Author

Wesley Ivan Hurt, Jul 24 2019

Status

approved