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

Author

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

Keywords

• nonn

Examples

			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.
		

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

Programs

Haskell

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

Formula

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

Extensions

Offset fixed by Reinhard Zumkeller, Apr 03 2012