A039636 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, 3, 2, 1, 3, 1, 2, 2, 4, 1, 4, 1, 3, 3, 2, 1, 4, 4, 2, 2, 3, 1, 3, 1, 5, 5, 2, 2, 5, 1, 2, 2, 4, 1, 4, 1, 3, 3, 2, 1, 5, 5, 5, 5, 3, 1, 3, 3, 4, 4, 2, 1, 4, 1, 2, 2, 6, 6, 6, 1, 3, 3, 3, 1, 6, 1, 2, 2, 3, 3, 3, 1, 5, 5, 2, 1, 5, 5, 2, 2, 4, 1, 4, 4, 3, 3, 2, 2, 6, 1, 6, 6, 6, 1, 6

Offset

1,4

Links

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

Mathematica

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

Prog

(Haskell)
a039636 1 = 1
a039636 n = snd $ until ((== 1) . a010051 . fst)
                        (\(x, i) -> (x `div` 2 , i + 1)) (n, 1)
-- Reinhard Zumkeller, Nov 17 2013

Crossrefs

Cf. A039634-A039645.

Cf. A010051, A039634, A039637, A039642, A039643.

Sequence in context: A275761 A232396 A270096 * A322866 A328847 A331175

Adjacent sequences: A039633 A039634 A039635 * A039637 A039638 A039639

Keyword

nonn

Author

Wouter Meeussen

Extensions

Offset corrected by Reinhard Zumkeller, Nov 17 2013

Status

approved