A378660 Smallest divisor d of n for which n/d is non-abundant, i.e. sigma(n/d) <= 2*(n/d).

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 3, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 4, 1, 1, 1, 4, 1, 2, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 4, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 8, 1, 1, 1, 1, 1, 2, 1, 5, 1, 1, 1, 3, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 3, 1, 1, 1, 2, 1, 2, 1, 2, 1

Offset: 1

Author

Antti Karttunen, Dec 06 2024

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..100000

Crossrefs

Cf. A000203, A263837, A294935, A378665.

Programs

PARI

A294935(n) = (sigma(n)<=(2*n));
A378660(n) = { fordiv(n,d,if(A294935(n/d), return(d))); (n); };

Formula

a(n) = n / A378665(n).