A307348 Numbers k such that there are no palindromic triangular numbers of length k.

12, 30, 40, 47, 48, 50, 56, 60

Offset

1,1

Comments

Numbers k such that A054263(k) = 0. - Max Alekseyev, Jun 03 2026

Links

Table of n, a(n) for n=1..8.

Patrick De Geest, Palindromic Triangulars

Eric Weisstein's World of Mathematics, Palindromic Number

Mathematica

A003098 = Select[PolygonalNumber[3, Range[0, 10^6]], PalindromeQ];
(* Set Range to level of desired running time. *)
nopal[n_] := Length[Select[A003098, IntegerLength[#] == n || (n == 1 && # == 0) &]]; Select[Range[12], nopal[#] == 0 &]
(* Set Range to encompass length of last value in A003098. *)

Crossrefs

Cf. A000217, A003098, A008509, A054263, A034822, A307367.

Sequence in context: A115912 A083096 A289691 * A145469 A024364 A093507

Adjacent sequences: A307345 A307346 A307347 * A307349 A307350 A307351

Keyword

nonn,base,hard,more,changed

Author

Robert Price, May 01 2019

Extensions

a(4)-a(8) from Patrick De Geest's website added by Max Alekseyev, Jun 03 2026

Status

approved