cp's OEIS Frontend

A071177 Square-root of concatenation n'k, where k is minimal with n'k square (decimal notation).

%I A071177 #8 Feb 15 2023 14:02:28
%S A071177 4,5,6,7,23,8,27,9,31,10,34,11,37,12,39,13,42,43,14,45,46,15,152,156,
%T A071177 16,162,165,17,54,55,56,18,58,59,188,19,61,62,63,20,203,65,66,21,213,
%U A071177 68,69,22,222,71,72,23,73,74,235,75,24,242
%N A071177 Square-root of concatenation n'k, where k is minimal with n'k square (decimal notation).
%C A071177 a(n) = A000196(n'A071176(n))
%e A071177 a(5) = 23 as 23^2 = 529 = 5'29 and 5'i is nonsquare for i<29, A071176(5)=29.
%o A071177 (Python)
%o A071177 from math import isqrt
%o A071177 def A071177(n):
%o A071177     m = 10*n
%o A071177     if (k:=isqrt(m))**2!=m:
%o A071177         a = 1
%o A071177         while (k:=isqrt(a*(m+1)-1)+1)**2-m*a>=10*a:
%o A071177             a *= 10
%o A071177     return k # _Chai Wah Wu_, Feb 15 2023
%K A071177 nonn,base
%O A071177 1,1
%A A071177 _Reinhard Zumkeller_, May 15 2002