A179627 a(n) = length of Collatz sequence starting with n-th prime

2, 6, 5, 12, 11, 8, 10, 15, 12, 14, 68, 16, 70, 21, 67, 10, 23, 15, 20, 66, 74, 25, 71, 22, 76, 19, 57, 65, 73, 11, 32, 21, 59, 29, 18, 13, 26, 18, 45, 23, 23, 15, 31, 77, 20, 77, 28, 47, 12, 25, 55, 36, 17, 44, 79, 52, 22, 30, 14, 30, 41, 76, 27, 57, 84, 27, 19, 73, 81, 24, 81

Offset

1,1

Links

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

Eric Weisstein's World of Mathematics, Collatz Problem

Wikipedia, Collatz conjecture

Index entries for sequences related to 3x+1 (or Collatz) problem

Formula

a(n) = A006666(A000040(n)) + 1. [Reinhard Zumkeller, Apr 03 2012]

Example

For n=4 the a(n)=12 because the fourth prime is 7 and if you start with 7, the 12th term of syracuse-sequence is 1. The syracuse-sequence starting with 7 has the dimension 12.

Prog

(Haskell)
a179627 = (+ 1) . a006666 . a000040  -- Reinhard Zumkeller, Apr 03 2012

Crossrefs

Sequence in context: A077174 A211201 A359035 * A193977 A092313 A318358

Adjacent sequences: A179624 A179625 A179626 * A179628 A179629 A179630

Keyword

nonn

Author

Roland Schroeder (florola(AT)gmx.de), Jul 21 2010

Extensions

Offset fixed by Reinhard Zumkeller, Apr 03 2012

Status

approved