A081599 Let n = 10x + y where 0 <= y <= 9, x >= 0. Then a(n) = 8x+y.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 56, 57, 58, 59, 60, 61

Offset: 0

Author

N. J. A. Sloane, Apr 22 2003

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,0,0,0,0,0,1,-1).

Crossrefs

Cf. A081502. Different from A028898.

Programs

Magma

k:=8; [n-(10-k)*Floor(n/10): n in [0..100]]; // Bruno Berselli, Jun 24 2014

Maple

A081599 := proc(n)
    local x,y ;
    x := floor(n/10) ;
    y := modp(n,10) ;
    8*x+y ;
end proc:
seq(A081599(n),n=0..100) ; # R. J. Mathar, May 25 2023

Mathematica

Table[n-2*Floor[n/10],{n,0,80}] (* Harvey P. Dale, Nov 07 2017 *)

PARI

my(n, x, y); vector(200, n, y=(n-1)%10; x=(n-1-y)\10; 8*x+y) \\ Colin Barker, Jun 24 2014

Formula

G.f.: -x*(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 - 2*floor(n/10). - Bruno Berselli, Jun 24 2014