A131570 a(1) = 1; for n >= 1, if a(n) is odd then a(n+1) = a(n) followed by a(n)+1, but if a(n) is even then a(n+1) = a(n)/2.

1, 12, 6, 3, 34, 17, 1718, 859, 859860, 429930, 214965, 214965214966, 107482607483, 107482607483107482607484, 53741303741553741303742, 26870651870776870651871, 2687065187077687065187126870651870776870651872

Offset

1,2

Links

Table of n, a(n) for n=1..17.

Example

17 is odd so the next term is 1718; 1718 is even so the next term is 1718/2 = 859.

Maple

catL := proc(a, b) a*10^( max(ilog10(b)+1, 1)) +b ; end: A131570 := proc(n) option remember ; local prev; if n = 1 then 1 ; else prev := A131570(n-1) ; if prev mod 2 = 1 then catL(prev, prev+1) ; else prev/2 ; fi ; fi ; end: seq(A131570(n), n=1..20) ; # R. J. Mathar, Oct 26 2007

Mathematica

a = {1}; Do[If[OddQ[a[[ -1]]], AppendTo[a, FromDigits[Join[IntegerDigits[a[[ -1]]], IntegerDigits[a[[ -1]] + 1]]]], AppendTo[a, a[[ -1]]/2]], {25}]; a (* Stefan Steinerberger, Oct 26 2007 *)

Crossrefs

Sequence in context: A028578 A013680 A033963 * A033332 A051725 A070292

Adjacent sequences: A131567 A131568 A131569 * A131571 A131572 A131573

Keyword

nonn,base

Author

Rodolfo Kurchan, Aug 27 2007

Extensions

More terms from R. J. Mathar and Stefan Steinerberger, Oct 26 2007

Status

approved