A034980 a(n)^2 is smallest positive square starting with a string of n 2's.

1, 5, 15, 149, 4714, 47141, 471405, 1490712, 1490712, 471404521, 1490711985, 1490711985, 1490711985, 1490711985, 47140452079103, 149071198499986, 149071198499986, 14907119849998598, 14907119849998598, 471404520791031683, 14907119849998597976, 471404520791031682934, 4714045207910316829339

Offset: 0

Author

Patrick De Geest, Nov 15 1998

Keywords

• nonn
• base

Examples

			a(5)^2 = 47141^2 = {22222}73881.
		

Links

• Robert Israel, Table of n, a(n) for n = 0..996

Crossrefs

Cf. A034981.

Programs

Maple

f:= proc(n) local x, k, s;
  x:= 2*(10^n-1)/9;
  for k from 0 do
    s:= ceil(sqrt(10^k*x));
    if s^2 < (x+1)*10^k then return s fi
  od
end proc:
f(0):= 1:
map(f, [$0..30]); # Robert Israel, May 31 2023

Extensions

More terms from Francisco Salinas (franciscodesalinas(AT)hotmail.com), Dec 23 2001