A110756 a(n) = tau(N), where N = concatenation 1,2,3,...,n.

1, 6, 4, 4, 8, 28, 4, 24, 12, 8, 64, 32, 8, 8, 8, 12, 24, 48, 64, 192, 256, 64, 16, 48, 24, 160, 96, 64, 16, 128, 8, 48, 64, 4, 192, 120, 16, 16, 64, 384, 32, 128, 16, 48, 768, 128, 32, 192, 64, 768, 8, 32, 64, 1792, 32, 24, 64, 16, 16, 128, 8, 192, 24, 768, 64

Offset

1,2

Links

Tyler Busby, Table of n, a(n) for n = 1..117

Formula

a(n) = A000005(A007908(n)). - R. J. Mathar, Feb 10 2007

Example

a(3) = tau(123) = 4.

Maple

A055642 := proc(n) 1+floor(log10(n)) ; end; A000005 := proc(n) numtheory[tau](n) ; end ; A007908 := proc(n) local a ; a := 1 ; for i from 2 to n do a := a*10^A055642(i)+i ; end; RETURN(a) ; end; A110756 := proc(n) A000005(A007908(n)) ; end; for n from 1 to 50 do printf("%d %d ", n, A110756(n)) ; od ; # R. J. Mathar, Feb 10 2007

Mathematica

Table[DivisorSigma[0, FromDigits[Flatten[IntegerDigits/@Range[n]]]], {n, 60}] (* Harvey P. Dale, Apr 01 2024 *)

Crossrefs

Cf. A000005, A007908, A110757, A110758, A110759, A110760.

Sequence in context: A021612 A329281 A201587 * A200698 A013661 A209273

Adjacent sequences: A110753 A110754 A110755 * A110757 A110758 A110759

Keyword

nonn,base

Author

Amarnath Murthy, Aug 11 2005

Extensions

More terms from R. J. Mathar, Feb 10 2007

More terms from David Wasserman, Dec 22 2008

a(57)-a(65) from Jinyuan Wang, May 23 2020

Status

approved