A307367 Number of palindromic triangular numbers with exactly n digits.

4, 2, 3, 3, 2, 2, 6, 2, 1, 4, 7, 0, 4, 4, 12, 5, 6, 2, 3, 2, 6, 3, 6, 2, 2, 4, 3, 2, 5, 0, 3, 2, 1, 4, 3, 1, 10, 1, 4, 0, 3, 2, 2, 1, 3, 3, 0, 0, 9, 0, 3, 2, 4, 3, 5, 0, 4, 2, 2, 0, 4, 7, 3

Offset

1,1

Comments

Number of terms in A003098 with exactly n digits.

Differs from A054263 only at a(1), assuming 0 has 1 digits. - R. J. Mathar, May 06 2019

Links

Table of n, a(n) for n=1..63.

Patrick De Geest, Palindromic Triangulars.

G. J. Simmons, Palindromic powers, J. Rec. Math., 3 (No. 2, 1970), 93-98. [Annotated scanned copy] See page 95.

Mathematica

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

Crossrefs

Cf. A000217, A003098, A008509, A034822, A263618, A307348.

Sequence in context: A106644 A345996 A190874 * A136626 A079623 A177864

Adjacent sequences: A307364 A307365 A307366 * A307368 A307369 A307370

Keyword

nonn,base,more

Author

Robert Price, May 01 2019

Extensions

a(45) corrected, a(46)-a(63) from Patrick De Geest's website added by Max Alekseyev, Jun 03 2026

Status

approved