OFFSET
1,3
LINKS
Eric Weisstein's World of Mathematics, Refactorable Number
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, 0, 200}]]
PROG
(PARI) isok(n) = n%numdiv(n) == 0;
is(n) = sum(j=1, n-1, isok(j)&&isok(n-j)) == 0; \\ Jinyuan Wang, Jul 27 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jul 27 2019
STATUS
approved