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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A131760 Numbers n such that n multiplied by its reverse yields a fourth power. 1
1, 4, 9, 121, 484, 676, 2178, 8712, 10000, 10201, 12321, 14641, 40000, 40804, 44944, 69696, 90000, 94249, 698896, 1002001, 1210000, 1234321, 4008004, 4840000, 5221225, 6760000, 6948496, 21780000, 87120000, 100000000, 100020001 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence contains palindromic squares and palindromic squares with trailing zeros. Are 2178 and 8721 the only non-palindromic reversible pair in this sequence without trailing zeros?

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..108

EXAMPLE

2178 = 2*9*121 and 8712 = 8*9*121, 2718*8712 = (2*3*11)^4.

MATHEMATICA

Select[Range[1000000], IntegerQ[(#*FromDigits[Reverse[IntegerDigits[ # ]]])^(1/4)] &]

CROSSREFS

Cf. A002779 = Palindromic squares.

Sequence in context: A115667 A229971 A158642 * A002779 A028817 A057136

Adjacent sequences:  A131757 A131758 A131759 * A131761 A131762 A131763

KEYWORD

nonn,base

AUTHOR

Tanya Khovanova, Sep 17 2007

EXTENSIONS

a(20)-a(31) from Donovan Johnson, Oct 27 2008

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 March 29 12:56 EDT 2017. Contains 284270 sequences.