

A275473


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


0



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
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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: A240199 A094728 A212001 * A131805 A197694 A187770
Adjacent sequences: A275470 A275471 A275472 * A275474 A275475 A275476


KEYWORD

nonn


AUTHOR

Altug Alkan, Jul 29 2016


STATUS

approved



