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

1,3

Comments

Cycles with a period of length 9.

Links

Table of n, a(n) for n=1..110.

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 *)

Crossrefs

Cf. A000045, A175723, A020639, A178095.

Sequence in context: A272636 A066949 A073481 * A364874 A122556 A175723

Adjacent sequences: A178091 A178092 A178093 * A178095 A178096 A178097

Keyword

nonn

Author

N. J. A. Sloane, Dec 16 2010

Status

approved