A308065 Nonnegative integers that are not the sum of two refactorable numbers whose difference is refactorable.

0, 1, 2, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74

Offset

1,3

Links

Table of n, a(n) for n=1..67.

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, 0, 100}]]

Crossrefs

Cf. A033950, A309347.

Sequence in context: A026485 A294662 A183301 * A047318 A057904 A188397

Adjacent sequences: A308062 A308063 A308064 * A308066 A308067 A308068

Keyword

nonn

Author

Wesley Ivan Hurt, Jul 27 2019

Status

approved