A087843 a(n) = a(n - a(n-1)) + a(a(a(n - a(n-2)))).

1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 7, 6, 7, 7, 7, 7, 7, 9, 7, 9, 8, 9, 9, 9, 9, 9, 11, 9, 11, 9, 11, 10, 11, 11, 11, 11, 11, 13, 11, 13, 11, 13, 11, 13, 12, 13, 13, 13, 13, 13, 16, 13, 15, 13, 16, 15, 15, 13, 16, 16, 15, 16, 16, 16, 16, 16, 19, 16, 18, 16, 19, 18, 19, 19, 18

Offset

1,3

Comments

The fourth recursive of HofstadterQ second term of A005185.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

f:= proc(n) option remember; procname(n-procname(n-1)) + procname(procname(procname(n-procname(n-2)))); end proc:
f(1):= 1: f(2):=1:
map(f, [$1..100]); # Robert Israel, Dec 10 2024

Mathematica

Hofstadter[n_Integer?Positive] := Hofstadter[n] = Hofstadter[n - Hofstadter[n-1]] + Hofstadter[Hofstadter[Hofstadter[n - Hofstadter[n-2]]]] Hofstadter[1] = Hofstadter[2] = 1 digits=200 a1=Table[Hofstadter[n], {n, 1, digits}]

Crossrefs

Cf. A005185, A081831.

Sequence in context: A130148 A341510 A196238 * A087831 A351960 A372759

Adjacent sequences: A087840 A087841 A087842 * A087844 A087845 A087846

Keyword

nonn,look

Author

Roger L. Bagula, Oct 07 2003

Status

approved