

A263618


Number of palindromic squares with exactly n digits.


8



4, 0, 3, 0, 7, 1, 5, 0, 11, 0, 5, 1, 19, 0, 13, 1, 25, 0, 18, 0, 48, 1, 31, 0, 70, 1, 44, 2, 105, 0, 70, 1, 153, 1, 98, 3, 209, 0, 132, 0, 291, 1, 181, 1
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

Number of terms in A002779 with exactly n digits.
a(24) = a(30) = a(38) = a(40) = 0.  Robert Price, Apr 26 2019


LINKS

Table of n, a(n) for n=1..44.
G. J. Simmons, Palindromic powers, J. Rec. Math., 3 (No. 2, 1970), 9398. [Annotated scanned copy] See page 95.


MATHEMATICA

Table[Length[Select[Range[If[n == 1, 0, Ceiling[Sqrt[10^(n  1)]]], Floor[Sqrt[10^n]]], #^2 == IntegerReverse[#^2] &]], {n, 15}] (* Robert Price, Apr 26 2019 *)


CROSSREFS

Cf. A002778, A002779, A263617, A263617, A263619, A263620.
Sequence in context: A327305 A290328 A200682 * A156788 A130801 A280579
Adjacent sequences: A263615 A263616 A263617 * A263619 A263620 A263621


KEYWORD

nonn,base,more


AUTHOR

N. J. A. Sloane, Oct 23 2015


EXTENSIONS

a(13)a(19) from Chai Wah Wu, Oct 24 2015
a(20) from Robert Price, Apr 26 2019
a(21)a(44) (using A002778) from Chai Wah Wu, Sep 16 2021


STATUS

approved



