A178094 a(1)=a(2)=1; thereafter a(n) = lpf(a(n-1)+a(n-2)), where lpf = "least prime factor".

1, 1, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7, 2, 3, 5, 2, 7, 3, 2, 5, 7

Offset: 1

Author

N. J. A. Sloane, Dec 16 2010

Keywords

• nonn

Comments

Cycles with a period of length 9.

Crossrefs

Cf. A000045, A175723, A020639, A178095.

Programs

Mathematica

nxt[{a_,b_}]:={b,FactorInteger[a+b][[1,1]]}; NestList[nxt,{1,1},110][[;;,1]] (* or *) PadRight[ {1,1},110,{5,7,2,3,5,2,7,3,2}] (* Harvey P. Dale, May 29 2023 *)