A058425 Numbers k such that k^2 contains only digits {0,2,5}, not ending with zero.

5, 15, 45, 235, 505, 745, 1415, 1485, 4495, 5005, 15985, 50005, 72495, 469255, 500005, 500505, 1597505, 1598515, 4474955, 5000005, 5000505, 5050005, 7085235, 15008515, 44949995, 50000005, 50000505, 50005005, 50500005, 500000005, 500000505, 500005005, 500254955, 500500005

Offset: 1

Author

Patrick De Geest, Nov 15 2000

Keywords

• nonn
• base

Comments

Most terms have a special pattern in that they have only digits 0 and 5 and could be written as Sum_{h=0..t} 5*10^f(h), where 2f(h), 2f(h)-1, and f(h1) + f(h2) are all distinct and f(0)=0 for the nonzero ending constraint. - Zhao Hui Du, Mar 12 2024

Links

• Zhao Hui Du, Table of n, a(n) for n = 1..5913
• Patrick De Geest, Index to related sequences.
• Hisanori Mishima, Sporadic tridigital solutions.

Crossrefs

Cf. A058426.

Extensions

a(29)=50500005 inserted by Georg Fischer, Jan 12 2022