A264647 Smallest number m such that A263856(m) = n.

1, 2, 6, 4, 10, 8, 79, 199, 9, 108, 11, 29, 17, 15, 40, 80, 20, 59, 306, 22, 169, 38, 27, 82, 287, 41, 49, 209, 47, 135, 31, 36, 127, 112, 123, 162, 46, 89, 63, 54, 581, 43, 56, 770, 67, 48, 134, 52, 142, 69, 58, 101, 382, 466, 75, 64, 273, 95, 117, 126, 72

Offset: 1

Author

Reinhard Zumkeller, Nov 19 2015

Keywords

• nonn

Comments

a(6949) > 22700000 if it exists. - Chai Wah Wu, Feb 01 2016

Links

• Reinhard Zumkeller and Chai Wah Wu, Table of n, a(n) for n = 1..6948 n = 1..391 from Reinhard Zumkeller

Crossrefs

Cf. A263856.

Programs

Haskell

import Data.List (elemIndex); import Data.Maybe (fromJust)
a264647 = (+ 1) . fromJust . (`elemIndex` a263856_list)

Mathematica

f[p_] := f[p] = StringJoin @@ ToString /@ Reverse[IntegerDigits[p, 2]];
S[n_] := S[n] = SortBy[Prime[Range[n]], f];
A263856[n_] := A263856[n] = FirstPosition[S[n], Prime[n]][[1]];
a[n_] := a[n] = For[m = 1, True, m++, If[A263856[m] == n, Return[m]]];
Table[Print[n, " ", a[n]]; a[n], {n, 1, 391}] (* Jean-François Alcover, Sep 22 2021 *)

Formula

A263856(a(n)) = n and A263856(m) != n for m < a(n).