A232746 n occurs A030124(n) times; a(n) = one less than the least k such that A005228(k) > n.

1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10

Offset: 1

Author

Antti Karttunen, Nov 30 2013

Keywords

• nonn

Comments

The characteristic function for Hofstadter's A005228 is given by X_A005228(1)=1, and for n>1, X_A005228(n) = a(n)-a(n-1).

The characteristic function for Hofstadter's A030124 is given by X_A030124(1)=0, and for n>1, X_A030124(n) = 1-(a(n)-a(n-1)).

Useful when computing A232747, A232748, A232750 & A225850.

Links

• Index entries for Hofstadter-type sequences

Crossrefs

Cf. A005228, A030124, A232747, A232748, A232750, A232753, A225850.

Programs

Mathematica

nmax = 100; A5228 = {1}; Module[{d = 2, k = 1}, Do[While[MemberQ[A5228, d], d++]; k += d; d++; AppendTo[A5228, k], {n, 1, nmax}]];
a[n_] := For[k = 1, True, k++, If[A5228[[k]] > n, Return[k-1]]];
Array[a, nmax] (* Jean-François Alcover, Dec 09 2021 *)

Formula

a(n) = one less than the least k such that A005228(k) > n.