A109214 Product of a(n-1) and digit reversal of a(n-2).
1, 2, 2, 4, 8, 32, 256, 5888, 3838976, 34109301760, 231888097227054080, 1556059601911449331359933440, 125186119679477750610733678211850458005934080, 55507466796083630515105997822341552764197877620395801846452095434158080
Offset: 1
Crossrefs
Programs
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Maple
R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n): a:= proc(n) option remember; `if`(n<3, n, a(n-1)*R(a(n-2))) end: seq(a(n), n=1..14); # Alois P. Heinz, Sep 01 2025 -
Mathematica
a[1]=1;a[2]=2;a[n_]:=a[n]=a[n-1]*FromDigits[Reverse[IntegerDigits[a[n-2]]]]; A109214=Table[a[n], {n, 13}] Transpose[NestList[{Last[#],Last[#]FromDigits[Reverse[ IntegerDigits[ First[ #]]]]}&,{1,2},13]][[1]] (* Harvey P. Dale, Nov 14 2011 *)
Formula
a(n) = a(n-1)*R(a(n-2)).
Extensions
One more term (a(14)) from Harvey P. Dale, Nov 14 2011
Comments