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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 FrÃ¶hlich, 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.)