A081597 Let n = 10*x + y where 0 <= y <= 9, x >= 0. Then a(n) = 6*x + y.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 42, 43, 44, 45, 46, 47

Offset

0,3

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..2000

Formula

G.f.: -x*(3*x^9 -x^8 -x^7 -x^6 -x^5 -x^4 -x^3 -x^2 -x -1) / ((x -1)^2*(x +1)*(x^4 -x^3 +x^2 -x +1)*(x^4 +x^3 +x^2 +x +1)). - Colin Barker, Jun 24 2014

a(n) = n - 4*floor(n/10). [Bruno Berselli, Jun 24 2014]

a(n) = a(n-1) + a(n-10) - a(n-11) for n > 10. - Chai Wah Wu, Apr 25 2017

Maple

A081597:=n->n-4*floor(n/10): seq(A081597(n), n=0..150); # Wesley Ivan Hurt, Apr 25 2017

Mathematica

CoefficientList[Series[-x (3 x^9 - x^8 - x^7 - x^6 - x^5 - x^4 - x^3 - x^2 - x - 1)/((x - 1)^2 (x + 1) (x^4 - x^3 + x^2 - x + 1) (x^4 + x^3 + x^2 + x + 1)), {x, 0, 150}], x] (* Vincenzo Librandi, Jun 25 2014 *)

Prog

(PARI) my(n, x, y); vector(200, n, y=(n-1)%10; x=(n-1-y)\10; 6*x+y) \\ Colin Barker, Jun 24 2014
(Magma) k:=6; [n-(10-k)*Floor(n/10): n in [0..10]]; // Bruno Berselli, Jun 24 2014

Crossrefs

Cf. A081502. Different from A028901.

Sequence in context: A079827 A216196 A028901 * A351578 A328469 A373229

Adjacent sequences: A081594 A081595 A081596 * A081598 A081599 A081600

Keyword

nonn,easy

Author

N. J. A. Sloane, Apr 22 2003

Status

approved