A028869 Squares of primes with digits in descending order.

4, 9, 841, 961

Offset

1,1

Comments

No other solutions below 4 * 10^18 (probably finite). - Dec 15 1999

Links

Table of n, a(n) for n=1..4.

Example

961 = 31^2 is in the sequence since its digits (9, 6, 1) are in descending order.
1369 = 37^2 is not in the sequence, since its digits in descending order are: 9, 6, 3, 1.

Mathematica

Select[Prime[Range[100]]^2, IntegerDigits[#] == Sort[IntegerDigits[#], Less] &] (* Alonso del Arte, Aug 12 2016 *)

Crossrefs

Cf. A028868, A028865, A028866.

Sequence in context: A027522 A330580 A254959 * A179935 A073172 A168139

Adjacent sequences: A028866 A028867 A028868 * A028870 A028871 A028872

Keyword

nonn,base,hard,more

Author

Patrick De Geest

Extensions

Offset changed by Altug Alkan, Sep 09 2016

Status

approved