

A027829


Palindromic squares with an even number of digits.


2



698896, 637832238736, 4099923883299904, 6916103777337773016196, 40460195511188111559106404, 4872133543202112023453312784, 9658137819052882509187318569, 46501623417708833880771432610564, 1635977102407987117897042017795361
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OFFSET

1,1


REFERENCES

C. Ashbacher, More on palindromic squares, J. Rec. Math. 22, no. 2 (1990), 133135. [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), 124132. [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



