A068666 a(1) = 5; a(n) = smallest palindromic multiple of a(n-1).

5, 55, 5005, 55055, 50155105, 5065665605, 50155155155105, 5464353998993534645, 541025148469303964841520145, 513016415223221833242338122322514610315

Offset: 1

Author

Amarnath Murthy, Mar 01 2002

Keywords

• base
• nonn
• more

Crossrefs

Cf. A068664, A068665, A068667, A068668, A070069, A068971, A068972, A068973, A068974.

Programs

Mathematica

a[1] = 5; a[n_] := a[n] = Block[{k = 2}, While[k*a[n - 1] != ToExpression[ StringReverse[ ToString[k*a[n - 1]]]], k++ ]; k*a[n - 1]]; Table[a[n], {n, 1, 9}]
spm[n_]:=Module[{k=2},While[!PalindromeQ[k*n],k++];k*n]; NestList[spm,5,10] (* Harvey P. Dale, Nov 10 2022 *)

Extensions

Corrected and extended by David W. Wilson and Patrick De Geest, Mar 30 2002

a(10) from John Gustaf Stebbins, Sep 17 2008