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A309347 Numbers that are the sum of two refactorable numbers whose difference is refactorable. 1
3, 10, 17, 27, 36, 48, 54, 60, 84, 88, 96, 104, 108, 112, 120, 128, 132, 136, 144, 152, 156, 168, 176, 180, 184, 192, 200, 204, 208, 216, 224, 228, 232, 240, 248, 252, 256, 264, 272, 276, 280, 288, 296, 300, 304, 312, 324, 328, 336, 344, 348, 352, 360, 368 (list; graph; refs; listen; history; text; internal format)
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/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, 400}]]

CROSSREFS

Cf. A033950.

Sequence in context: A219726 A017017 A297665 * A273235 A309351 A003615

Adjacent sequences:  A309344 A309345 A309346 * A309348 A309349 A309350

KEYWORD

nonn

AUTHOR

Wesley Ivan Hurt, Jul 24 2019

STATUS

approved

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Last modified March 29 21:32 EDT 2020. Contains 333117 sequences. (Running on oeis4.)