login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A027829 Palindromic squares with an even number of digits. 2
698896, 637832238736, 4099923883299904, 6916103777337773016196, 40460195511188111559106404, 4872133543202112023453312784, 9658137819052882509187318569, 46501623417708833880771432610564, 1635977102407987117897042017795361 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

C. Ashbacher, More on palindromic squares, J. Rec. Math. 22, no. 2 (1990), 133-135. [A scan of the first page of this article is included with the last page of the Keith (1990) scan]

LINKS

M. F. Hasler, Table of n, a(n) for n = 1..13

K. S. Brown, On General Palindromic Numbers

P. De Geest, Palindromic Squares

P. De Geest, Subsets of Palindromic Squares

M. Keith, Classification and enumeration of palindromic squares, J. Rec. Math., 22 (No. 2, 1990), 124-132. [Annotated scanned copy]

FORMULA

a(n) = A016113(n)^2. - M. F. Hasler, Jun 08 2014

PROG

(PARI) is_A027829(n)={issquare(n)&&vecextract(n=digits(n), "-1..1")==n&&!bittest(#n, 0)} \\ This is faster than first checking for even length if applied to numbers known to have an even number of digits, as should be the case for a systematic search. In the latter case, one should actually only consider squares, i.e., rather use is_A016113.  - M. F. Hasler, Jun 08 2014

CROSSREFS

Cf. A002113, A002778, A002779, A016113.

Sequence in context: A114676 A205608 A205439 * A258129 A204496 A183835

Adjacent sequences:  A027826 A027827 A027828 * A027830 A027831 A027832

KEYWORD

nonn,base

AUTHOR

Keith Devlin, via Boon Leong (boon_leong(AT)hotmail.com)

EXTENSIONS

2 new terms were recently found by Bennett from UK (communication from Patrick De Geest, Dec. 1999 or before).

Edited by M. F. Hasler, Jun 08 2014

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy .

Last modified January 22 22:34 EST 2018. Contains 298093 sequences.