A262279 Smallest m such that A261923(m) = n.

0, 1, 2, 6, 75

Offset: 0

Author

Reinhard Zumkeller, Sep 17 2015

Keywords

• nonn
• more

Comments

A261923(m) != 5 for m <= 10^5.

The same for m <= 5*10^8. - Michel Marcus, Sep 20 2023

From Michael S. Branicky, Sep 21 2023: (Start)

a(5) <= 10718873460460617403023221866359404479.

a(n) exists for all n. Proof. Let b(i) be the binary representation of i. Let L be its length, and w = 0^L be a string of L 0's. Then a(n+1) <= u = b(1)wb(2)w...wb(a(n)-1)_2 since u's binary representation contains that of each number less than a(n) but not that of a(n). So, A261923(u) = 1 + A261923(a(n)). (End)

Crossrefs

Cf. A056744, A261923.

Programs

Haskell

import Data.List (elemIndex); import Data.Maybe (fromJust)
a262279 = fromJust . (`elemIndex` a261923_list)

PARI

a(n) = my(k=0); while (A261923(k) != n, k++); k; \\ Michel Marcus, Sep 20 2023