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A115539
Numbers k such that the concatenation of k with 5*k gives a square.
0
2040816326530612245, 8163265306122448980, 18367346938775510205, 265008112493239588967009194159005, 346133044889129259058950784207680, 438074634937804218496484586262845, 540832882639264467279610600324500
OFFSET
1,1
EXAMPLE
2040816326530612245_10204081632653061225 = 14285714285714285715^2.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Jan 25 2006
STATUS
approved