A248512 Sequence based on repeating in turn the subtract, add and multiply operations on the previous 2 terms, starting with 0, 1.

0, 1, 1, 2, 2, 0, 2, 0, -2, -2, 4, 6, 10, 60, 50, 110, 5500, 5390, 10890, 58697100, 58686210, 117383310, 6888781581155100, 6888781463771790, 13777563044926890, 94910620919839581404684194433100, 94910620919839567627121149506210

Offset: 1

Author

Stuart E Anderson, Oct 07 2014

Keywords

• sign
• easy

Comments

After a(16) the sequence entries end 100, 90, 90, 100, 10, 10, 100, 90, 90, ... . - Jon Perry, Oct 29 2014

Programs

Mathematica

nxt[{n_,a_,b_}]:={n+1,b,Which[Mod[n+1,3]==0,b-a,Mod[n+1,3] == 1,a+b,True,a*b]}; NestList[nxt,{2,0,1},30][[All,2]] (* Harvey P. Dale, Sep 20 2021 *)

Formula

For n > 2,

If n mod 3 = 0, a(n) = a(n-1) - a(n-2),

If n mod 3 = 1, a(n) = a(n-1) + a(n-2),

If n mod 3 = 2, a(n) = a(n-1) x a(n-2),

a(1) = 0, a(2) = 1.

Extensions

More terms from Colin Barker, Oct 08 2014

Edited: Name changed and keyword easy added - Wolfdieter Lang, Oct 29 2014

Changed name. - Jon Perry, Oct 29 2014