A202342 - OEIS

%I #24 Jan 17 2025 19:32:02

%S 1,4,5,7,10,13,14,17,18,20,23,24,26,29,32,33,35,38,41,42,45,46,48,51,

%T 54,55,58,59,61,64,65,67,70,73,74,77,78,80,83,84,86,89,92,93,95,98,

%U 101,102,105,106,108,111,112,114,117,120,121,123,126,129,130,133

%N Numbers occurring exactly twice in Hofstadter H-sequence A005374.

%C A202340(a(n)) = 2.

%H Reinhard Zumkeller, <a href="/A202342/b202342.txt">Table of n, a(n) for n = 1..10000</a>

%H Larry Ericksen and Peter G. Anderson, <a href="http://www.cs.rit.edu/~pga/k-zeck.pdf">Patterns in differences between rows in k-Zeckendorf arrays</a>, The Fibonacci Quarterly, Vol. 50, No. 1 (February 2012), pp. 11-18.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HofstadterH-Sequence.html">Hofstadter H-Sequence.</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Hofstadter_sequence">Hofstadter sequence</a>

%H <a href="/index/Ho#Hofstadter">Index entries for Hofstadter-type sequences</a>

%F a(n) = A005374(A136496(n)). - _Alan Michael Gómez Calderón_, Dec 22 2024

%F a(n) = A136495(A136495(n)). - _Alan Michael Gómez Calderón_, Jan 06 2025

%o (Haskell)

%o import Data.List (elemIndices)

%o a202342 n = a202342_list !! (n-1)

%o a202342_list = elemIndices 2 a202340_list

%Y Cf. A005374, A202340, A136495, A136496, A202341 (complement).

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Dec 17 2011