A039637 Number of steps to fixed point of "n -> n/2 or (n+1)/2 until result is prime".

1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 3, 1, 2, 4, 4, 1, 3, 1, 3, 2, 2, 1, 4, 2, 2, 3, 3, 1, 5, 1, 5, 2, 2, 4, 4, 1, 2, 4, 4, 1, 3, 1, 3, 2, 2, 1, 5, 3, 3, 3, 3, 1, 4, 4, 4, 2, 2, 1, 6, 1, 2, 6, 6, 3, 3, 1, 3, 5, 5, 1, 5, 1, 2, 3, 3, 5, 5, 1, 5, 2, 2, 1, 4, 2, 2, 4, 4, 1, 3, 3, 3, 2, 2, 6, 6, 1, 4, 4, 4, 1, 4

Offset

1,4

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Mathematica

upplist[ n_Integer ] := Length/@Drop[ FixedPointList[ If[ EvenQ[ # ]&&#>2, #/ 2, If[ PrimeQ[ # ]||(#===1), #, (#+1)/2 ] ]&, n, 20 ], -1 ]

Prog

(Haskell)
a039637 1 = 1
a039637 n = snd $ until ((== 1) . a010051 . fst)
                        (\(x, i) -> ((x + 1) `div` 2 , i + 1)) (n, 1)
-- Reinhard Zumkeller, Nov 17 2013

Crossrefs

Cf. A039634-A039645.

Cf. A010051, A039635, A039636, A039644, A039645.

Sequence in context: A323436 A056692 A331600 * A194548 A274009 A069157

Adjacent sequences: A039634 A039635 A039636 * A039638 A039639 A039640

Keyword

nonn

Author

Wouter Meeussen

Extensions

Offset corrected by Reinhard Zumkeller, Nov 17 2013

Status

approved