A173455 Row sums of triangle A027751.

1, 1, 1, 3, 1, 6, 1, 7, 4, 8, 1, 16, 1, 10, 9, 15, 1, 21, 1, 22, 11, 14, 1, 36, 6, 16, 13, 28, 1, 42, 1, 31, 15, 20, 13, 55, 1, 22, 17, 50, 1, 54, 1, 40, 33, 26, 1, 76, 8, 43, 21, 46, 1, 66, 17, 64, 23, 32, 1, 108, 1, 34, 41, 63, 19, 78, 1, 58, 27, 74, 1, 123, 1, 40, 49, 64, 19, 90, 1, 106

Offset: 1

Author

Omar E. Pol, Nov 22 2010

Keywords

• nonn

Comments

Essentially the same as A001065, but with a(1)=1.

Note that if n is a noncomposite number then a(n)=1.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..4096

Crossrefs

Cf. A001065, A008578, A027751.

Programs

Mathematica

Array[Boole[# == 1] + DivisorSigma[1, #] - # &, 80] (* Michael De Vlieger, Oct 30 2017 *)

PARI

a(n) = if (n==1, 1, sigma(n) - n); \\ Michel Marcus, Oct 30 2017