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A241217 Largest number that when multiplied by 7 produces an n-digit number. 1
1, 14, 142, 1428, 14285, 142857, 1428571, 14285714, 142857142, 1428571428, 14285714285, 142857142857, 1428571428571, 14285714285714, 142857142857142, 1428571428571428, 14285714285714285, 142857142857142857, 1428571428571428571, 14285714285714285714 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The definition "largest number that when multiplied by 3 produces an n-digit number" gives A002277.

LINKS

Table of n, a(n) for n=1..20.

Index entries for linear recurrences with constant coefficients, signature (11,-10,-1,11,-10).

FORMULA

a(n) = floor(10^n/7). - Michel Marcus, Apr 21 2014

G.f.: x*(1+3*x-2*x^2+7*x^3)/((x-1)*(10*x-1)*(x+1)*(x^2-x+1)). - Alois P. Heinz, Apr 30 2014

EXAMPLE

14*7 = 98 but 15*7 = 105 (too large) so a(2) = 14.

PROG

(PARI) a(n) = floor(10^n/7); \\ Michel Marcus, Apr 21 2014

CROSSREFS

Cf. A020806, A002277.

Sequence in context: A011547 A011548 A039916 * A159500 A167834 A238473

Adjacent sequences:  A241214 A241215 A241216 * A241218 A241219 A241220

KEYWORD

nonn,base,easy

AUTHOR

J. Lowell, Apr 17 2014

EXTENSIONS

More terms from Michel Marcus, Apr 21 2014

STATUS

approved

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Last modified September 18 16:05 EDT 2020. Contains 337169 sequences. (Running on oeis4.)