A134871 a(1) = 1, a(n) = tau(n) + n - 2 for n > 1.

1, 2, 3, 5, 5, 8, 7, 10, 10, 12, 11, 16, 13, 16, 17, 19, 17, 22, 19, 24, 23, 24, 23, 30, 26, 28, 29, 32, 29, 36, 31, 36, 35, 36, 37, 43, 37, 40, 41, 46, 41, 48, 43, 48, 49, 48, 47, 56, 50, 54, 53, 56, 53, 60, 57, 62, 59, 60, 59, 70, 61, 64, 67, 69, 67, 72, 67

Offset: 1

Author

Gary W. Adamson, Nov 14 2007

Keywords

• nonn

Examples

			a(4) = 5 = sum of row 4 terms of triangle A134870: (1 + 2 + 1 + 1).
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..1000

Crossrefs

Row sums of A134870.

Cf. A000005 (tau), A071324, A051731.

Programs

Mathematica

a[1]=1;a[n_]:=DivisorSigma[0,n]+n-2;Array[a,67] (* James C. McMahon, Apr 10 2025 *)

PARI

a(n)={numdiv(n) + n - 1 - (n>1)} \\ Andrew Howroyd, Aug 10 2018

Extensions

Name changed, a(12) corrected and a(15)-a(67) from Andrew Howroyd, Aug 10 2018