A039642 -id:A039642 - cp's OEIS frontend

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

Wouter Meeussen

nonn

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

Cf. A039634-A039645.

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

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

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

Offset corrected by Reinhard Zumkeller, Nov 17 2013

A039644 Number of steps to fixed point of "k -> k/2 or (k+1)/2 until result is prime", starting with prime(n)-1.

Original entry on oeis.org

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

Offset: 1

Wouter Meeussen

nonn

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

Cf. A039634-A039645.

Cf. A010051, A000040, A039640, A039642, A039637.

a039644 1 = 1
a039644 n = snd $ until ((== 1) . a010051 . fst)
            (\(x, i) -> ((x + 1) `div` 2 , i + 1)) (a000040 n - 1, 1)
-- Reinhard Zumkeller, Nov 17 2013

Mathematica
```
(* See A039637. *)
```

Offset corrected by Reinhard Zumkeller, Nov 17 2013

A039638 Fixed point of "k -> k/2 or (k-1)/2 until result is prime", starting with prime(n)-1.

Original entry on oeis.org

1, 2, 2, 3, 5, 3, 2, 2, 11, 7, 7, 2, 5, 5, 23, 13, 29, 7, 2, 17, 2, 19, 41, 11, 3, 3, 3, 53, 13, 7, 31, 2, 17, 17, 37, 37, 19, 5, 83, 43, 89, 11, 47, 3, 3, 3, 13, 13, 113, 7, 29, 59, 7, 31, 2, 131, 67, 67, 17, 17, 17, 73, 19, 19, 19, 79, 41, 5, 173, 43, 11, 179, 11, 23, 47, 191

Offset: 1

Wouter Meeussen

nonn

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

Cf. A039634-A039645.

Cf. A010051, A000040, A039642, A039640, A039634.

a039638 1 = 1
a039638 n = until ((== 1) . a010051) (flip div 2) (a000040 n - 1)
-- Reinhard Zumkeller, Nov 17 2013

(* See A039634. *)
Table[NestWhile[If[EvenQ[#],#/2,(#-1)/2]&,Prime[n]-1,CompositeQ],{n,80}] (* Harvey P. Dale, May 27 2023 *)

Offset corrected by Reinhard Zumkeller, Nov 17 2013

cp's OEIS Frontend

A039636 Number of steps to fixed point of "n -> n/2 or (n-1)/2 until result is prime".

Views

Author

Keywords

Links

Crossrefs

Programs

Haskell

Mathematica

Extensions

A039644 Number of steps to fixed point of "k -> k/2 or (k+1)/2 until result is prime", starting with prime(n)-1.

Views

Author

Keywords

Links

Crossrefs

Programs

Haskell

Mathematica

Extensions

A039638 Fixed point of "k -> k/2 or (k-1)/2 until result is prime", starting with prime(n)-1.

Views

Author

Keywords

Links

Crossrefs

Programs

Haskell

Mathematica

Extensions