A110757 a(n) = number of divisors of N, where N = reverse concatenation of 1,2,3,...,n.

1, 4, 4, 4, 8, 4, 4, 12, 18, 8, 4, 8, 8, 16, 48, 16, 96, 576, 16, 32, 16, 32, 16, 32, 64, 256, 96, 32, 128, 256, 8, 64, 32, 128, 384, 144, 16, 8, 64, 32, 256, 64, 8, 192, 96, 32, 128, 128, 8, 64, 8, 128, 1280, 2560, 8, 24, 16, 64, 8, 8, 32, 384, 48, 64, 128, 128

Offset

1,2

Links

Tyler Busby, Table of n, a(n) for n = 1..106

Formula

a(n) = A000005(A000422(n)). - Jinyuan Wang, May 23 2020

Example

a(3) = tau(321) = 4.

Mathematica

s = ""; Do[s = ToString[n] <> s; Print[DivisorSigma[0, ToExpression[s]]], {n, 1, 45}] (* Ryan Propper, Sep 23 2005 *)
Table[DivisorSigma[0, FromDigits[Flatten[IntegerDigits/@Range[n, 1, -1]]]], {n, 50}] (* The program takes a long time to run. *) (* Harvey P. Dale, Jun 06 2018 *)

Crossrefs

Cf. A000005, A000422, A176024.

Cf. A110756, A110758, A110759, A110760.

Sequence in context: A342484 A105352 A132200 * A167184 A276113 A232406

Adjacent sequences: A110754 A110755 A110756 * A110758 A110759 A110760

Keyword

nonn,base

Author

Amarnath Murthy, Aug 11 2005

Extensions

More terms from Ryan Propper, Sep 23 2005

a(46)-a(66) from Jinyuan Wang, May 23 2020

Status

approved