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A176385 The smallest number which when multiplied by the n-th repunit gives a Smith number. 1
4, 2, 6, 56, 32, 97, 6, 95, 176, 4, 32, 309, 68, 68, 194, 616, 175, 96, 1540, 4, 816, 14, 1540, 95, 840, 32, 5, 437, 50, 10336, 95, 5, 995, 976, 175, 14, 40, 570, 1976, 995, 1400, 294, 1994, 176, 544, 507, 328, 392, 77, 11020, 18905, 18050, 9995, 779, 4, 805, 669 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Smith numbers, A006753: the digits-sum equals the digits-sum of its prime factors.

Repunits: R(n)=(10^n-1)/9 = A002275(n).

LINKS

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

EXAMPLE

R(3)=111 multiplied by a(3)=6 yields z=666=2*3*3*37 = A006753(34): 6+6+6 = 2+3+3+3+7 = 18.

MAPLE

# digits-sum of primfactors of z=dsp(z)

for n from 2 to 70 do f(n):=1: test:=false:

while (f(n) < 420000) and (test=false) do

f(n):=f(n)+1: z:=f(n)*r(n): ds(z):=0:

dsp(z):=dsp(r(n))+dsp(f(n)):

while (z>0) do z:=iquo(z, 10, 'm'): ds(z):=ds(z)+m: end do:

if(ds(z)=dsp(z)) then test:=true: print(n, f(n)): end if:

end do: end do:

CROSSREFS

Sequence in context: A019105 A183399 A248250 * A155829 A181051 A299631

Adjacent sequences:  A176382 A176383 A176384 * A176386 A176387 A176388

KEYWORD

nonn,base

AUTHOR

Paul Weisenhorn, Apr 16 2010, Apr 23 2010

EXTENSIONS

Keyword:base added by R. J. Mathar, Apr 24 2010

STATUS

approved

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Last modified May 19 22:32 EDT 2019. Contains 323411 sequences. (Running on oeis4.)