A064426 First differences of A064413.

1, 2, 2, -3, 6, 3, -4, 2, -5, 10, 3, -4, -7, 14, 3, -8, 4, 2, -11, 22, -6, 3, -5, 10, -7, -2, -13, 26, -3, -4, 2, -17, 34, -9, -4, -19, 38, -12, -5, 4, 2, -23, 46, -21, 2, 2, 2, 2, -7, 14, -3, -5, 10, 5, -12, -29, 58, -21, -4, -31, 62, -21, -8, 4, 6, -37, 74, -36, 3, -2, 4, 2, -41, 82, -42, 3, -7, 11, -2, -43

Offset: 1

Author

N. J. A. Sloane, Oct 02 2001

Keywords

• sign

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, Exper. Math. 11 (2002), 437-446.
• Index entries for sequences related to EKG sequence

Programs

Haskell

a064426 n = a064426_list !! (n-1)
a064426_list = zipWith (-) (tail a064413_list) a064413_list
-- Reinhard Zumkeller, Sep 17 2001

Mathematica

ekg[s_] := Block[{m = s[[-1]], k = 3}, While[MemberQ[s, k] || GCD[m, k] == 1, k++]; Append[s, k]]; Nest[ekg, {1, 2}, 100] // Differences (* Jean-François Alcover, Sep 10 2018, after Robert G. Wilson v *)