A047906 a(n+1) = a(n) - n (if n is odd), a(n+1) = a(n) * n (if n is even).

1, 0, 0, -3, -12, -17, -102, -109, -872, -881, -8810, -8821, -105852, -105865, -1482110, -1482125, -23714000, -23714017, -426852306, -426852325, -8537046500, -8537046521, -187815023462, -187815023485, -4507560563640

Offset

1,4

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..500

Mathematica

Transpose[NestList[{First[#]+1, If[OddQ[First[#]], Last[#]-First[#], Last[#]*First[#]]}&, {1, 1}, 30]][[2]] (* Harvey P. Dale, Dec 12 2011 *)
nxt[{n_, a_}]:={n+1, If[OddQ[n], a-n, a*n]}; NestList[nxt, {1, 1}, 40][[;; , 2]] (* Harvey P. Dale, May 25 2024 *)

Prog

(Haskell)
a047906 n = a047906_list !! (n-1)
a047906_list = 1 : zipWith uncurry
                           (cycle [(-), (*)]) (zip a047906_list [1..])
-- Reinhard Zumkeller, Nov 14 2013

Crossrefs

Cf. A000124, A000142, A047907.

Sequence in context: A045549 A103249 A354680 * A342776 A104641 A032703

Adjacent sequences: A047903 A047904 A047905 * A047907 A047908 A047909

Keyword

sign,easy,nice

Author

Miklos SZABO (mike(AT)ludens.elte.hu)

Status

approved