A309351 Sums of two distinct refactorable numbers whose product and difference are refactorable.

3, 10, 17, 36, 60, 84, 88, 96, 104, 108, 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, 372, 376, 384, 392, 396, 400, 408, 420, 424, 444, 456, 459, 468, 472

Offset

1,1

Links

Table of n, a(n) for n=1..53.

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 - 1)/2]}] > 0, n, {}], {n, 500}]]

Crossrefs

Cf. A033950.

Sequence in context: A309347 A273235 A334964 * A003615 A043293 A208894

Adjacent sequences: A309348 A309349 A309350 * A309352 A309353 A309354

Keyword

nonn

Author

Wesley Ivan Hurt, Jul 24 2019

Status

approved