OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Refactorable Number
EXAMPLE
3 is in the sequence since 3 = 1 + 2 and both 1 and 2 are refactorable (since d(1) = 1 | 1 and d(2) = 2 | 2).
4 is in the sequence since 4 = 2 + 2 and 2 is refactorable (since d(2) | 2).
MATHEMATICA
Flatten[Table[If[Sum[ (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/2]}] > 0, n, {}], {n, 100}]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jul 24 2019
STATUS
approved