A092404 a(n) = phi(n) + phi(n+1).

2, 3, 4, 6, 6, 8, 10, 10, 10, 14, 14, 16, 18, 14, 16, 24, 22, 24, 26, 20, 22, 32, 30, 28, 32, 30, 30, 40, 36, 38, 46, 36, 36, 40, 36, 48, 54, 42, 40, 56, 52, 54, 62, 44, 46, 68, 62, 58, 62, 52, 56, 76, 70, 58, 64, 60, 64, 86, 74, 76

Offset: 1

Author

Jon Perry, Mar 22 2004

Keywords

• nonn
• easy

Comments

A054521 is the following array A read along antidiagonals:

1, 0, 0, 0, 0, 0, ...

1, 1, 1, 1, 1, 1, ...

1, 0, 1, 0, 1, 0, ...

1, 1, 0, 1, 1, 0, ...

1, 0, 1, 0, 1, 0, ...

1, 1, 1, 1, 0, 1, ...

and a(n) is apparently the hook sum Sum_{k=0..n} A(n,k) + Sum_{r=0..n-1} A(r,n). - R. J. Mathar, Jun 30 2013

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000010, A054521.

Programs

Mathematica

Table[(EulerPhi[n] + EulerPhi[n + 1]), {n, 60}] (* Vincenzo Librandi, Sep 27 2013 *)
Total/@Partition[EulerPhi[Range[70]],2,1] (* Harvey P. Dale, Dec 30 2015 *)

PARI

for(i=1,60,print1(","eulerphi(i)+eulerphi(i+1)))