cp's OEIS Frontend

A110754 a(n) = tau(N), where N = the number obtained as a concatenation of 8712 with itself n times and tau(n) = number of divisors of n.

%I A110754 #14 Nov 09 2019 16:27:09
%S A110754 36,144,768,576,1152,6144,2304,18432,15360,18432,12288,49152,4608,
%T A110754 36864,6291456,294912,9216,983040,576,294912,18874368,196608,9216,
%U A110754 25165824,1179648,73728,2359296,1179648,73728,402653184,2304,2359296,33554432,147456,75497472,31457280,147456,36864
%N A110754 a(n) = tau(N), where N = the number obtained as a concatenation of 8712 with itself n times and tau(n) = number of divisors of n.
%C A110754 8712 has the property that any number of concatenation of it with self and the digit reversal have same prime divisors.
%F A110754 a(n) = A000005(8712*Sum_{i=0..n-1} 10^(4i)). - _R. J. Mathar_, Aug 17 2007
%e A110754 a(2) = tau(87128712) = 144.
%p A110754 A110754 := proc(n) local pow8712,i ; pow8712 := 8712*add(10^(4*i),i=0..n-1) ; numtheory[tau](pow8712) ; end: seq(A110754(n),n=1..22) ; # _R. J. Mathar_, Aug 17 2007
%t A110754 Table[DivisorSigma[0,FromDigits[PadRight[{},4n,{8,7,1,2}]]],{n,25}] (* _Harvey P. Dale_, Dec 29 2016 *)
%o A110754 (PARI) a(n)={numdiv(8712*(10^(4*n)-1)/9999)} \\ _Andrew Howroyd_, Nov 09 2019
%Y A110754 Cf. A110751, A110752, A110753.
%K A110754 base,nonn
%O A110754 1,1
%A A110754 _Amarnath Murthy_, Aug 11 2005
%E A110754 More terms from _R. J. Mathar_, Aug 17 2007
%E A110754 a(23)-a(38) from _Andrew Howroyd_, Nov 09 2019