A039642 Number of steps to fixed point of "k -> k/2 or (k-1)/2 until result is prime", starting with prime(n)-1.

1, 1, 2, 2, 2, 3, 4, 4, 2, 3, 3, 5, 4, 4, 2, 3, 2, 4, 6, 3, 6, 3, 2, 4, 6, 6, 6, 2, 4, 5, 3, 7, 4, 4, 3, 3, 4, 6, 2, 3, 2, 5, 3, 7, 7, 7, 5, 5, 2, 6, 4, 3, 6, 4, 8, 2, 3, 3, 5, 5, 5, 3, 5, 5, 5, 3, 4, 7, 2, 4, 6, 2, 6, 5, 4, 2, 3, 8, 8, 8, 6, 6, 3, 6, 3, 6, 7, 7, 7, 7, 2, 2, 7, 4, 5, 2, 3, 9, 9, 4, 6, 3

Offset

1,3

Links

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

Mathematica

see A039636.

Prog

(Haskell)
a039642 1 = 1
a039642 n = snd $ until ((== 1) . a010051 . fst)
                  (\(x, i) -> (x `div` 2 , i + 1)) (a000040 n - 1, 1)
-- Reinhard Zumkeller, Nov 17 2013

Crossrefs

Cf. A039634-A039645.

Cf. A010051, A000040, A039638, A039644, A039636.

Sequence in context: A243322 A071454 A178139 * A027300 A085313 A065458

Adjacent sequences: A039639 A039640 A039641 * A039643 A039644 A039645

Keyword

nonn

Author

Wouter Meeussen

Extensions

Offset corrected by Reinhard Zumkeller, Nov 17 2013

Status

approved