

A247264


Smallest positive number not divisible by 10 whose square remains a square when prefixed with 10^n.


4




OFFSET

0,1


LINKS

Table of n, a(n) for n=0..5.


EXAMPLE

a(0) = 15 since 15^2 = 225 and 1225 is square and 15 is the smallest number not ending in 0 with this property. a(3) = 375 since 375^2 = 140625 and 1000140625 is square and 375 is the smallest number not ending in 0 with this property.


PROG

(PARI)
a(n)=k=1; while(k^2%100==0!issquare(10^(#Str(k^2)+n)+k^2), k++); k^2
n=0; while(n<10, print1(a(n), ", "); n++) \\ Derek Orr, Sep 13 2014


CROSSREFS

Cf. A242268, A247261, A247262, A247263, A247312.
Sequence in context: A007328 A222909 A049391 * A212093 A212241 A000477
Adjacent sequences: A247261 A247262 A247263 * A247265 A247266 A247267


KEYWORD

nonn,base


AUTHOR

Chai Wah Wu, Sep 11 2014


STATUS

approved



