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A214893
Conway's subprime Fibonacci sequence starting with (18, 5).
1
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
Richard K. Guy, Tanya Khovanova and Julian Salazar, Conway's subprime Fibonacci sequences, arXiv:1207.5099v1 [math.NT]
MATHEMATICA
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 *)
KEYWORD
nonn
AUTHOR
Wouter Meeussen, Jul 29 2012
STATUS
approved