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A182686 a(n) = the largest n-digit number with exactly 13 divisors, a(n) = 0 if no such number exists. 2
0, 0, 0, 4096, 0, 531441, 0, 0, 244140625, 0, 13841287201, 0, 3138428376721, 23298085122481, 582622237229761, 2213314919066161, 21914624432020321, 787662783788549761, 6582952005840035281, 39959630797262576401 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

a(n) = the largest n-digit number of the form p^12 (p = prime), a(n) = 0 if no such number exists.

LINKS

Robert Israel, Table of n, a(n) for n = 1..999

FORMULA

A000005(a(n)) = 13.

a(n) = A182685(n) for n <= 17.

MAPLE

f:= proc(n) local r;

  r:= prevprime(ceil(10^(n/12)))^12;

  if r < 10^(n-1) then 0 else r fi;

end proc:

f(1):= 0: f(2):= 0: f(3):=0:

map(f, [$1..30]); # Robert Israel, Apr 03 2019

PROG

(PARI) a(n) = my(r=precprime(ceil(10^(n/12))-1)^12); if(r < 10^(n-1), return(0)); r \\ Adapted from Robert Israel's Maple program; Felix Fröhlich, Apr 03 2019

CROSSREFS

Cf. A030631, A182685.

Sequence in context: A212935 A076154 A182685 * A176768 A223601 A186490

Adjacent sequences:  A182683 A182684 A182685 * A182687 A182688 A182689

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Nov 27 2010

STATUS

approved

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Last modified September 23 11:53 EDT 2020. Contains 337310 sequences. (Running on oeis4.)