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A308494
Refactorable numbers k such that the number of divisors of k-1 also divides k.
0
8, 12, 18, 24, 36, 40, 56, 60, 72, 80, 84, 88, 96, 104, 108, 128, 132, 136, 152, 156, 180, 184, 204, 228, 232, 240, 248, 252, 276, 288, 296, 328, 344, 348, 360, 372, 376, 384, 396, 444, 448, 450, 468, 472, 480, 488, 492, 504, 516, 536, 560, 564, 584, 600
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Refactorable Number
MATHEMATICA
Flatten[Table[If[Sum[(1 - Ceiling[n/DivisorSigma[0, n]] + Floor[n/DivisorSigma[0, n]]) (1 - Ceiling[n/DivisorSigma[0, n - 1]] + Floor[n/DivisorSigma[0, n - 1]]) , {i, Floor[(n - 1)/2]}] > 0, n, {}], {n, 0, 600}]]
CROSSREFS
Cf. A033950.
Sequence in context: A085103 A280968 A157940 * A087696 A293529 A028393
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jul 27 2019
STATUS
approved