A145011 First differences of A007775.

6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 2, 4, 6, 2

Offset: 1

Author

Ki Punches, Feb 25 2009

Keywords

• nonn
• easy

Comments

Also the first differences of A084968 divided by 7. - Antti Karttunen, May 01 2015

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,1).

Crossrefs

Cf. A007775, A084968.

Multiplied by 7: row 4 of A257251.

Programs

Haskell

a145011 n = a145011_list !! (n-1)
a145011_list = zipWith (-) (tail a007775_list) a007775_list
-- Reinhard Zumkeller, Jan 06 2013

Mathematica

Differences[Select[Range[400],GCD[#,30]==1&]] (* Harvey P. Dale, Dec 07 2011 *)

PARI

a(n)=[4,6,4,2,4,2][n%8+1] \\ Charles R Greathouse IV, Oct 20 2013

Formula

Period 8: repeat 6,4,2,4,2,4,6,2.

a(n) = 2*((abs(abs((n mod 8) - 3) - 1) mod 3) + 1). - Pieter Stadhouders, Mar 09 2010

G.f.: x*(-2*x^7 - 6*x^6 - 4*x^5 - 2*x^4 - 4*x^3 - 2*x^2 - 4*x - 6)/(x^8 - 1). - Chai Wah Wu, Feb 16 2021

Extensions

Edited by Omar E. Pol, Mar 02 2009

Offset corrected by Reinhard Zumkeller, Jan 06 2013