A202342 Numbers occurring exactly twice in Hofstadter H-sequence A005374.

1, 4, 5, 7, 10, 13, 14, 17, 18, 20, 23, 24, 26, 29, 32, 33, 35, 38, 41, 42, 45, 46, 48, 51, 54, 55, 58, 59, 61, 64, 65, 67, 70, 73, 74, 77, 78, 80, 83, 84, 86, 89, 92, 93, 95, 98, 101, 102, 105, 106, 108, 111, 112, 114, 117, 120, 121, 123, 126, 129, 130, 133

Offset: 1

Author

Reinhard Zumkeller, Dec 17 2011

Keywords

• nonn

Comments

Position of the n-th occurrence of the digit 1 in A105083(n-1) for n>=1. - Jeffrey Shallit, Mar 08 2025

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Larry Ericksen and Peter G. Anderson, Patterns in differences between rows in k-Zeckendorf arrays, The Fibonacci Quarterly, Vol. 50, No. 1 (February 2012), pp. 11-18.
• Jeffrey Shallit, The Narayana Morphism and Related Words, arXiv:2503.01026 [math.CO], 2025.
• Eric Weisstein's World of Mathematics, Hofstadter H-Sequence.
• Wikipedia, Hofstadter sequence
• Index entries for Hofstadter-type sequences

Crossrefs

Cf. A005374, A105083, A202340, A136495, A136496, A202341 (complement).

Programs

Haskell

import Data.List (elemIndices)
a202342 n = a202342_list !! (n-1)
a202342_list = elemIndices 2 a202340_list

Formula

A202340(a(n)) = 2.

a(n) = A005374(A136496(n)). - Alan Michael Gómez Calderón, Dec 22 2024

a(n) = A136495(A136495(n)). - Alan Michael Gómez Calderón, Jan 06 2025