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A105582 Smallest composite number n such that every divisor > 1 includes n as a substring. 0

%I

%S 10201,121,254,39,1849,25,16043,497,6889,1691,10201,111221,16129,

%T 13169,214411,1532801,516221,117589,1401847,19361,2520899,44521,

%U 512231,235129,582497,628253,726031,395279,802817,295639,921307,31961,4320991,143323

%N Smallest composite number n such that every divisor > 1 includes n as a substring.

%C All entries so far are semiprimes (A001358), some are perfect powers (A001597). - _Robert G. Wilson v_, May 09 2005

%t fQ[n_, i_] := Block[{d = ToString /@ Drop[ Divisors[n], 1]}, Union[ StringPosition[d, ToString[i]]][[1]] != {}]; Do[k = 2; While[ PrimeQ[k] || fQ[k, n] == False, k++ ]; Print[k], {n, 0, 31}] (* _Robert G. Wilson v_, May 09 2005 *)

%K nonn,base

%O 0,1

%A _David W. Wilson_, May 08 2005

%E More terms from _Robert G. Wilson v_, May 09 2005

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Last modified August 24 13:48 EDT 2019. Contains 326279 sequences. (Running on oeis4.)