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A307367 Number of palindromic triangular numbers with exactly n digits. 1
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, 1 (list; graph; refs; listen; history; text; internal format)
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..45.

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: A073244 A106644 A190874 * A136626 A079623 A177864

Adjacent sequences:  A307364 A307365 A307366 * A307368 A307369 A307370

KEYWORD

nonn,base,more

AUTHOR

Robert Price, May 01 2019

STATUS

approved

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Last modified December 16 04:22 EST 2019. Contains 330013 sequences. (Running on oeis4.)