A131760 Numbers n such that n multiplied by its reverse yields a fourth power.

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

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 A319483

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