A247799 a(0) = 1; a(n) = a(n-1) + (if n = a(k) for some k then k else n).

0, 1, 3, 5, 9, 12, 18, 25, 33, 37, 47, 58, 63, 76, 90, 105, 121, 138, 144, 163, 183, 204, 226, 249, 273, 280, 306, 333, 361, 390, 420, 451, 483, 491, 525, 560, 596, 605, 643, 682, 722, 763, 805, 848, 892, 937, 983, 993, 1041, 1090, 1140, 1191, 1243, 1296

Offset

0,3

Comments

a(n) <= A000217(n).

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..1000

Prog

(Haskell)
import Data.List (elemIndex); import Data.Maybe (maybe)
a247799 n = a247799_list !! n
a247799_list = 0 : f 1 [0] where
   f x zs@(z:_) = y : f (x + 1) (y : zs) where
                  y = z + maybe x id (elemIndex x $ reverse zs)

Crossrefs

Cf. A000217.

Sequence in context: A005766 A211538 A368613 * A265702 A190310 A046746

Adjacent sequences: A247796 A247797 A247798 * A247800 A247801 A247802

Keyword

nonn

Author

Reinhard Zumkeller, Sep 26 2014

Status

approved