A275473 Least k such that d(k*n) = k, or 0 if no such k exists (d = A000005).

1, 4, 3, 9, 8, 12, 8, 10, 12, 18, 8, 20, 8, 18, 24, 8, 8, 0, 8, 24, 24, 18, 8, 16, 9, 18, 0, 20, 8, 0, 8, 14, 24, 18, 36, 24, 8, 18, 24, 16, 8, 40, 8, 20, 0, 18, 8, 24, 9, 36, 24, 20, 8, 18, 36, 16, 24, 18, 8, 32, 8, 18, 0, 0, 36, 40, 8, 20, 24, 48

Offset

1,2

Links

Table of n, a(n) for n=1..70.

Example

a(4) = 9 because A000005(9*4) = 9.

Mathematica

up[t_] := If[t < 15, 18, t^(1.066/Log[Log[t]])];  a[n_] := Catch@ Block[{k = 1}, While[ up[k*n]/k > 1, If[ DivisorSigma[0, k n] == k, Throw@ k, k++]]; 0]; Array[a, 70] (* Giovanni Resta, Jul 29 2016 *)

Crossrefs

Cf. A000005, A036763.

Sequence in context: A212001 A365904 A370290 * A131805 A197694 A187770

Adjacent sequences: A275470 A275471 A275472 * A275474 A275475 A275476

Keyword

nonn

Author

Altug Alkan, Jul 29 2016

Status

approved