A048350 a(n)^2 is the smallest square containing exactly n 5's.

5, 75, 235, 745, 22485, 22925, 235065, 505525, 2356384, 23569166, 227069495, 674919666, 3931354166, 7450205075, 39969432765, 524933839166, 2134374738666, 4904646324166, 23802428354166, 159861050770834, 725227930760773, 1882963768916666, 7586668936732745, 74536940878685015, 174801474694453186

Offset: 1

Author

Patrick De Geest, Mar 15 1999

Keywords

• nonn
• base

Links

• Eric Weisstein's World of Mathematics, Square Number

Crossrefs

Cf. A036512, A034986, A048351.

Programs

Mathematica

k := 1; For[n = 1, n < 30000, n++, If[DigitCount[n^2][[5]] == k, k++; Print[n]]] (* Stefan Steinerberger, Apr 09 2006 *)
a[n_] := Module[{i = 1}, While[DigitCount[i^2][[6]] != n, i++;]; i]; (* Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 20 2006 *)

Extensions

More terms from Jon E. Schoenfield, Jan 14 2009

One more term from Jon E. Schoenfield, Jan 25 2009

a(17)-a(19) from Giovanni Resta, Jul 27 2018

a(20)-a(25) from Max Alekseyev, Mar 06 2025