A318553 a(1) = 1, a(n) = -5*a(n/3) if n is divisible by 3, a(n) = n - a(n-1) if n + 1 is divisible by 3, otherwise a(n) = n + a(n-1).

1, 1, -5, -1, 6, -5, 2, 6, 25, 35, -24, 5, 18, -4, -30, -14, 31, 25, 44, -24, -10, 12, 11, -30, -5, 31, -125, -97, 126, -175, -144, 176, 120, 154, -119, -25, 12, 26, -90, -50, 91, 20, 63, -19, 150, 196, -149, 70, 119, -69, -155, -103, 156, -125, -70, 126, -220, -162, 221, 120, 181, -119, 50, 114, -49, -60, 7, 61

Offset: 1

Author

Altug Alkan, Aug 28 2018

Keywords

• sign
• look

Links

• Altug Alkan, Table of n, a(n) for n = 1..10934
• Altug Alkan, A scatterplot of a(n) for 4*3^8 <= n <= 5*3^8-1

Crossrefs

Cf. A305865.

Programs

Mathematica

a[1]=1; a[n_] := a[n] = Switch[Mod[n, 3], 0, -5 a[n/3], 1, n + a[n-1], 2, n - a[n-1]]; Array[a, 68] (* Giovanni Resta, Sep 05 2018 *)

PARI

a = vector(99); for(n=1, #a, print1 (a[n]=if(n<=1, 1, if (n%3==0, -5*a[n/3],if(n%3==1, n+a[n-1],n-a[n-1])))", "));

PARI

a(n) = if(n==1, 1, if(n%3==0, -5*a(n/3), if(n%3==1, n+a(n-1), n-a(n-1))))