1,4

It appears that (1) a(n)=0 if and only if n is a power of 2 and (2) a(n)=n-1 if and only if n+1 is a prime. (This has been verified for the first 2000 terms.

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

a(n) = A005408(n) - A000203(n+1). - Omar E. Pol, Jan 24 2014

(Haskell)

a120444 n = a120444_list !! (n-1)

a120444_list = zipWith (-) (tail a004125_list) a004125_list

-- Reinhard Zumkeller, May 30 2015

Cf. A000203, A004125, A005408.

Sequence in context: A143315 A237588 A235796 * A094919 A328373 A316631

Adjacent sequences: A120441 A120442 A120443 * A120445 A120446 A120447

sign

John W. Layman, Jul 19 2006

approved