cp's OEIS Frontend

A364444 a(n) is the number of integers k with n^2 < k < (n+1)^2 that are the sum of no more than 3 squares, counting multiple representations only once.

%I A364444 #12 Aug 01 2023 09:56:07
%S A364444 0,2,3,5,7,8,10,11,14,15,16,18,20,22,23,24,27,29,30,31,34,34,36,38,40,
%T A364444 42,44,44,47,48,49,51,54,55,57,58,61,61,62,65,67,69,69,71,73,75,76,78,
%U A364444 81,81,83,85,87,89,89,91,94,95,97,97,100,101,103,104,107,109
%N A364444 a(n) is the number of integers k with n^2 < k < (n+1)^2 that are the sum of no more than 3 squares, counting multiple representations only once.
%o A364444 (PARI) isA004215(n)= n\4^valuation(n, 4)%8==7 \\ after _M. F. Hasler_
%o A364444 a364444(n) = sum (k=n^2+1, n^2+2*n, !isA004215(k))
%o A364444 (Python)
%o A364444 def A364444(n): return sum(1 for k in range(n**2+1,(n+1)**2) if (m:=(~k&k-1).bit_length())&1 or (k>>m)&7<7) # _Chai Wah Wu_, Aug 01 2023
%Y A364444 Cf. A004215, A077773, A364445.
%K A364444 nonn
%O A364444 0,2
%A A364444 _Hugo Pfoertner_, Aug 01 2023