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A308065 Numbers k >= 0 that are not the sum of two refactorable numbers whose difference is refactorable. 4
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 12 21:22 EST 2019. Contains 329079 sequences. (Running on oeis4.)