A109213 Product of a(n-2) and digit reversal of a(n-1).

1, 2, 2, 4, 8, 32, 184, 15392, 5400584, 74651892640, 25003708306137848, 6335942056759761366725617280, 20682199297864337408779128828731176793076928

Offset

1,2

Comments

Cf. A000301 a(n) = a(n-1)*a(n-2), A004086 R(n) = digit reversal of n, A109214 a(n)=a(n-1)*R(a(n-2)).

Links

Table of n, a(n) for n=1..13.

Formula

a(n)=a(n-2)*R(a(n-1)).

Example

a(5)=8, a(6)=32, R(32)=23, hence a(7)=8*23=184; R(184)=841, a(8)=32*841=15392, etc.

Mathematica

a[1]=1; a[2]=2; a[n_]:=a[n]=a[n-2]*FromDigits[Reverse[IntegerDigits[a[n-1]]]]; A109213=Table[a[n], {n, 13}]
nxt[{a_, b_}]:={b, a*IntegerReverse[b]}; NestList[nxt, {1, 2}, 15][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 09 2017 *)

Crossrefs

Cf. A000301, A004086, A109214.

Sequence in context: A300759 A100799 A070323 * A109214 A000301 A124439

Adjacent sequences: A109210 A109211 A109212 * A109214 A109215 A109216

Keyword

base,nonn

Author

Zak Seidov, Jun 22 2005

Status

approved