A214893 Conway's subprime Fibonacci sequence starting with (18, 5).

18, 5, 23, 14, 37, 17, 27, 22, 7, 29, 18, 47, 13, 30, 43, 73, 58, 131, 63, 97, 80, 59, 139, 99, 119, 109, 114, 223, 337, 280, 617, 299, 458, 757, 405, 581, 493, 537, 515, 526, 347, 291, 319, 305, 312, 617, 929

Offset

1,1

Comments

Similar to the Fibonacci recursion starting with (18, 5), but each new nonprime term is divided by its least prime factor. Sequence enters a loop of length 56 after 26 terms on reaching (119, 109).

Links

Wouter Meeussen, Table of n, a(n) for n = 1..82

Richard K. Guy, Tanya Khovanova and Julian Salazar, Conway's subprime Fibonacci sequences, arXiv:1207.5099v1 [math.NT]

Mathematica

see A214674
nxt[{a_, b_}]:=Module[{c=a+b}, {b, If[PrimeQ[c], c, c/FactorInteger[c][[1, 1]]]}]; Transpose[NestList[nxt, {18, 5}, 82]][[1]] (* Harvey P. Dale, Oct 19 2012 *)

Crossrefs

Cf. A000045, A020639, A175723, A214551, A014682, A214674, A214892-A214898.

Sequence in context: A040314 A160486 A040312 * A065909 A352223 A186158

Adjacent sequences: A214890 A214891 A214892 * A214894 A214895 A214896

Keyword

nonn

Author

Wouter Meeussen, Jul 29 2012

Status

approved