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A069502 a(1) = 1; a(n) = smallest multiple of a(n-1) which is a palindromic triangular number. 1
1, 3, 6, 66, 8778, 6172882716 (list; graph; refs; listen; history; text; internal format)
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 A205081 A282175

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

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Last modified April 6 11:38 EDT 2020. Contains 333273 sequences. (Running on oeis4.)