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A195199 Smallest multiple of n with more than twice as many divisors as n. 2
4, 12, 12, 24, 20, 36, 28, 48, 36, 60, 44, 120, 52, 84, 60, 96, 68, 144, 76, 120, 84, 132, 92, 240, 100, 156, 108, 168, 116, 180, 124, 192, 132, 204, 140, 360, 148, 228, 156, 240, 164, 252, 172, 264, 180, 276, 188, 480, 196, 300, 204, 312, 212, 432, 220, 336 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..56.

FORMULA

a(n) = min{k*n: A000005(k*n) > 2*A000005(n)}.

EXAMPLE

a(4) must have more than 6 divisors because 4 has 3 divisors and 3*2=6. Therefore, it cannot be 16 because 16 has only 5 divisors.

MAPLE

A195199 := proc(n)

        for k from 2 do

                if numtheory[tau](k*n) > 2*numtheory[tau](n) then

                        return k*n ;

                end if;

        end do:

end proc: # R. J. Mathar, Oct 21 2011

MATHEMATICA

Table[d = DivisorSigma[0, n]; m = 1; While[DivisorSigma[0, m*n] <= 2*d, m++]; m*n, {n, 100}] (* T. D. Noe, Oct 21 2011 *)

CROSSREFS

Sequence in context: A005886 A096442 A211437 * A294628 A323188 A284126

Adjacent sequences:  A195196 A195197 A195198 * A195200 A195201 A195202

KEYWORD

nonn

AUTHOR

J. Lowell, Oct 12 2011

STATUS

approved

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Last modified February 20 07:54 EST 2020. Contains 332069 sequences. (Running on oeis4.)