A185137 Tri-recursive sequence: a(n) = a(a(a(n-1))) + a(n - a(a(-3+n))) if n>6, otherwise a(n) = 1.

1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 12, 13, 14, 15, 15, 15, 15, 15, 15, 16, 17, 18, 20, 20, 20, 20, 20, 20, 20, 21, 22, 23, 26, 26, 26, 26, 26, 26, 26, 26, 27

Offset

1,7

Comments

a(n-1) <= a(n) for n <= 64, but a(65)-a(64) = 32-35 < 0; first positions m where a(m) > a(m+1): 64, 79, 84, 99, 105, 106, 110, 125, 126, ... . - Reinhard Zumkeller, Jun 13 2013

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for Hofstadter-type sequences

Mathematica

a[1] = 1; a[2] = 1; a[3] = 1; a[4] = 1; a[5] = 1; a[6] = 1;
a[n_] := a[n] = a[a[a[n - 1]]] + a[n - a[a[-3 + n]]]
Table[a[n], {n, 1, 300}]

Prog

(Haskell)
a185137 n = a185137_list !! (n-1)
a185137_list = 1 : 1 : 1 : 1 : 1 : 1 : f 7 1 1 where
   f x u v = w : f (x + 1) v w where
             w = (a185137 . a185137 . a185137) (x - 1) +
                 a185137 (x - (a185137 . a185137) (x - 3))
-- Reinhard Zumkeller, Jun 13 2013

Crossrefs

Cf. A209384, A087831.

Sequence in context: A328865 A329623 A285762 * A368906 A368993 A137180

Adjacent sequences: A185134 A185135 A185136 * A185138 A185139 A185140

Keyword

nonn,look

Author

Roger L. Bagula, Mar 12 2012

Status

approved