A048349 a(n)^2 is the smallest square containing exactly n 4's.

2, 12, 38, 212, 2538, 6888, 66592, 210771, 2059962, 6696592, 21081538, 209868112, 664488107, 3800598038, 18613286762, 209820981888, 666669703412, 666516649788, 6666894662768, 49400874945738

Offset

1,1

Comments

a(21) > 10^14. - Giovanni Resta, Jul 27 2018

Links

Table of n, a(n) for n=1..20.

Eric Weisstein's World of Mathematics, Square Number

Mathematica

a[n_] := Block[{k=1}, While[DigitCount[k^2, 10, 4] != n, k++]; k]; Array[a, 7] (* Giovanni Resta, Jul 27 2018 *)

Crossrefs

Cf. A036511, A034984.

Sequence in context: A035597 A000913 A026575 * A009632 A190022 A086602

Adjacent sequences: A048346 A048347 A048348 * A048350 A048351 A048352

Keyword

nonn,base,more

Author

Patrick De Geest, Mar 15 1999

Extensions

More terms from Jon E. Schoenfield, Jan 14 2009

a(17)-a(20) from Giovanni Resta, Jul 27 2018

Status

approved