A251539 First differences of A251538.

4, 4, 4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 1, 1, 1, 1, 2, 4, 4, 4, 4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 4, 4

Offset: 1

Author

N. J. A. Sloane, Dec 07 2014

Keywords

• nonn

Comments

I would very much like to have a formula or recurrence for this sequence.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..100000

Crossrefs

Cf. A098548, A251535-A251538.

Cf. A251767 (duplicates removed), A251768 (run lengths).

Programs

Haskell

a251539 n = a251539_list !! (n-1)
a251539_list = zipWith (-) (tail a251538_list) a251538_list
-- Reinhard Zumkeller, Dec 08 2014

Mathematica

max = 1000 (* = max term of A251538 *);
A098548 = {1, 2, 3};
For[n = 4, n <= 8 max, n++, If[GCD[n, A098548[[-1]]] == 1 && GCD[n, A098548[[-2]]] > 1, AppendTo[A098548, n]]];
A251538 = Select[Range[max], A098548[[2#+3]] > A098548[[2#+1]] + 6&];
Differences[A251538] (* Jean-François Alcover, Aug 01 2018 *)