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 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. 2
 36, 144, 768, 576, 1152, 6144, 2304, 18432, 15360, 18432, 12288, 49152, 4608, 36864, 6291456, 294912, 9216, 983040, 576, 294912, 18874368, 196608, 9216, 25165824, 1179648, 73728, 2359296, 1179648, 73728, 402653184, 2304, 2359296, 33554432, 147456, 75497472, 31457280, 147456, 36864 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 8712 has the property that any number of concatenation of it with self and the digit reversal have same prime divisors. LINKS FORMULA a(n) = A000005(8712*Sum_{i=0..n-1} 10^(4i)). - R. J. Mathar, Aug 17 2007 EXAMPLE a(2) = tau(87128712) = 144. MAPLE 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 MATHEMATICA Table[DivisorSigma[0, FromDigits[PadRight[{}, 4n, {8, 7, 1, 2}]]], {n, 25}] (* Harvey P. Dale, Dec 29 2016 *) PROG (PARI) a(n)={numdiv(8712*(10^(4*n)-1)/9999)} \\ Andrew Howroyd, Nov 09 2019 CROSSREFS Cf. A110751, A110752, A110753. Sequence in context: A005017 A288488 A262789 * A299854 A154711 A162992 Adjacent sequences:  A110751 A110752 A110753 * A110755 A110756 A110757 KEYWORD base,nonn AUTHOR Amarnath Murthy, Aug 11 2005 EXTENSIONS More terms from R. J. Mathar, Aug 17 2007 a(23)-a(38) from Andrew Howroyd, Nov 09 2019 STATUS approved

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Last modified August 4 08:30 EDT 2021. Contains 346445 sequences. (Running on oeis4.)