A061468 a(n) = d(n) + phi(n), where d(n) is the number of divisors (A000005) and phi(n) is Euler's totient function (A000010).

2, 3, 4, 5, 6, 6, 8, 8, 9, 8, 12, 10, 14, 10, 12, 13, 18, 12, 20, 14, 16, 14, 24, 16, 23, 16, 22, 18, 30, 16, 32, 22, 24, 20, 28, 21, 38, 22, 28, 24, 42, 20, 44, 26, 30, 26, 48, 26, 45, 26, 36, 30, 54, 26, 44, 32, 40, 32, 60, 28, 62, 34, 42, 39, 52, 28

Offset: 1

Author

Amarnath Murthy, May 04 2001

Keywords

• nonn
• easy

Comments

If d(n) increases phi(n) tends to go down so the sum has a significance.

Examples

			a(20) = d(20) + phi(20) = 6 + 8 = 14.
		

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000005, A000010.

Programs

Maple

with(numtheory); A061468 := n-> tau(n) + phi(n);

Mathematica

Table[DivisorSigma[0,n]+EulerPhi[n],{n,70}] (* Harvey P. Dale, Aug 22 2020 *)

PARI

{ for (n=1, 1000, write("b061468.txt", n, " ", numdiv(n) + eulerphi(n)) ) } \\ Harry J. Smith, Jul 23 2009

Extensions

More terms from Winston C. Yang (winston(AT)cs.wisc.edu), May 19 2001