A069502 a(1) = 1; a(n) = smallest multiple of a(n-1) which is a palindromic triangular number.

1, 3, 6, 66, 8778, 6172882716

Offset

0,2

Comments

a(7) must be larger than 5*10^41. - Patrick De Geest

Links

Table of n, a(n) for n=0..5.

P. De Geest, List of palindromic triangulars

Mathematica

smpt[n_]:=Module[{k=2}, While[!PalindromeQ[k*n]||!OddQ[Sqrt[1+8*k*n]], k++]; k*n]; NestList[smpt, 1, 5] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 01 2019 *)

Crossrefs

Cf. A069501.

Sequence in context: A068665 A229236 A050722 * A296374 A362822 A205081

Adjacent sequences: A069499 A069500 A069501 * A069503 A069504 A069505

Keyword

nonn,base,hard

Author

Amarnath Murthy, Mar 30 2002

Extensions

a(6) from Patrick De Geest, Jun 11 2003

Status

approved