A048351 a(n)^2 is the smallest square containing exactly n 6's.

4, 26, 216, 1291, 5164, 68313, 163284, 785294, 3559026, 26393686, 129099069, 254296413, 816435342, 4081257976, 80413106314, 215329205326, 2463064689907, 5165911014784, 24832773982716, 81401883640163

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

Formula

a(n) = sqrt(A036513(n)).

Mathematica

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 *)

Prog

(Python)
def a(n):
  k = 1
  while not str(k**2).count('6') == n: k += 1
  return k
print([a(n) for n in range(1, 11)]) # Michael S. Branicky, Apr 26 2021

Crossrefs

Cf. A036513, A034988.

Sequence in context: A283828 A306028 A164101 * A224734 A143436 A135884

Adjacent sequences: A048348 A048349 A048350 * A048352 A048353 A048354

Keyword

nonn,base,more

Author

Patrick De Geest, Mar 15 1999

Extensions

816435342 from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 20 2006

a(14)-a(15) from Jon E. Schoenfield, Jan 14 2009

a(16) from Jon E. Schoenfield, Jan 24 2009

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

Status

approved