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

18, 72, 384, 288, 576, 3072, 1152, 9216, 7680, 9216, 6144, 24576, 2304, 18432, 3145728, 147456, 4608, 491520, 288, 147456, 9437184, 98304, 4608, 12582912, 589824, 36864, 1179648, 589824, 36864, 201326592

Offset: 1

Author

Amarnath Murthy, Aug 11 2005

Keywords

• base
• nonn

Comments

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.

Examples

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

Crossrefs

Cf. A110751, A110752.

Programs

Mathematica

k = 0; Do[k = (10^4 * k) + 2178; Print[DivisorSigma[0, k]], {n, 1, 30}] (* Ryan Propper, Aug 28 2005 *)
Table[DivisorSigma[0,FromDigits[PadRight[{},4n,{2,1,7,8}]]],{n,30}] (* Harvey P. Dale, Jun 23 2014 *)

Extensions

More terms from Ryan Propper, Aug 28 2005