A068664 a(1) = 1, a(n) = smallest palindromic multiple of a(n-1).

1, 2, 4, 8, 88, 616, 6776, 88088, 616616, 232464232, 21154245112, 232696696232, 21175399357112, 21154245133154245112, 232696696464696696232, 21175399378287399357112, 63386501441764911946714410568336

Offset: 1

Author

Amarnath Murthy, Mar 01 2002

Keywords

• base
• nonn

Crossrefs

A068667 (from a(3) on) and this sequence (from a(6) on) coincide.

Cf. A068665, A068666, A068667, A068668, A070069, A068971, A068972, A068973, A068974.

Programs

Mathematica

a=1; Print[a]; For[n = 2, n <= 15, n++, {an = a; k = 2; str = ToString[k*an]; rstr = StringReverse[str]; While[str != rstr, {k = k + 1; str = ToString[k*an]; rstr = StringReverse[str]; If[k*an > 10^20, {Print["Too big"]; Abort[]}]}]; a := k*an; Print[k, " ", a];}]
spm[n_]:=Module[{k=2},While[!PalindromeQ[k*n],k++];k*n]; NestList[spm,1,15] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 02 2019 *)

Extensions

Extended and edited by John W. Layman, Mar 18 2002

Last two terms from David W. Wilson and Patrick De Geest, Mar 30 2002