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A110753 a(n) is the number of divisors of the concatenation of 2178 with itself n times. 3

%I

%S 18,72,384,288,576,3072,1152,9216,7680,9216,6144,24576,2304,18432,

%T 3145728,147456,4608,491520,288,147456,9437184,98304,4608,12582912,

%U 589824,36864,1179648,589824,36864,201326592

%N a(n) is the number of divisors of the concatenation of 2178 with itself n times.

%C 2178 has the property that any number of concatenations of it with itself and its digit reversal have the same set of distinct prime factors.

%e a(2) = tau(21782178) = 72.

%t k = 0; Do[k = (10^4 * k) + 2178; Print[DivisorSigma[0, k]], {n, 1, 30}] (* _Ryan Propper_, Aug 28 2005 *)

%t Table[DivisorSigma[0,FromDigits[PadRight[{},4n,{2,1,7,8}]]],{n,30}] (* _Harvey P. Dale_, Jun 23 2014 *)

%Y Cf. A110751, A110752.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Aug 11 2005

%E More terms from _Ryan Propper_, Aug 28 2005

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Last modified September 16 18:26 EDT 2021. Contains 347473 sequences. (Running on oeis4.)