The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A263620 Number of nonzero palindromic squares with at most 2n digits. 3
 3, 6, 14, 19, 30, 36, 55, 69, 94, 112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS G. J. Simmons, Palindromic powers, J. Rec. Math., 3 (No. 2, 1970), 93-98. [Annotated scanned copy] See page 95. FORMULA Equals A263619(2n)-1. MATHEMATICA Table[Length[Select[Range[1, Floor[Sqrt[10^(2 n)]]], PalindromeQ[#^2] &]], {n, 6}] (* Robert Price, Apr 26 2019 *) PROG (Python) def ispal(n): s = str(n); return s == s[::-1] def a(n): c, k, kk = 0, 1, 1 while kk < 10**(2*n): c, k, kk = c + (ispal(kk)), k+1, kk + 2*k + 1 return c print([a(n) for n in range(1, 8)]) # Michael S. Branicky, Mar 06 2021 CROSSREFS Cf. A002778, A002779, A263617, A263617, A263618, A263619. Sequence in context: A075390 A118523 A097633 * A083356 A096337 A175318 Adjacent sequences: A263617 A263618 A263619 * A263621 A263622 A263623 KEYWORD nonn,base,more AUTHOR N. J. A. Sloane, Oct 23 2015 EXTENSIONS a(7)-a(10) from Chai Wah Wu, Oct 25 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 29 08:47 EST 2022. Contains 358422 sequences. (Running on oeis4.)