A332574 - OEIS

%I #7 Feb 17 2020 09:45:33

%S 127,631,751,1327,1527,1687,1711,2031,2047,2487,2647,3207,3271,3351,

%T 3511,3831,4567,4791,4911,5127,6007,6087,6711,7431,8247,8367,8391,

%U 8407,8551,8751,8871,9031,9447,9991,10407,10551,10887,10927,11631,12471,12567,12631,13807

%N Numbers k such that k, k + 1 and k + 2 are all norm-deficient in Gaussian integers (A332572).

%H Amiram Eldar, <a href="/A332574/b332574.txt">Table of n, a(n) for n = 1..10000</a>

%e 127 is a term since 127, 128 and 129 are all norm-deficient in Gaussian integers (A332572).

%t normDefQ[z_] := Abs[DivisorSigma[1, z, GaussianIntegers -> True]]^2 < 2*Abs[z]^2; Select[Range[10^4], AllTrue[# + Range[0, 2], normDefQ] &]

%Y Cf. A005100, A103228, A103229, A103230, A317047, A332572, A332573.

%K nonn

%O 1,1

%A _Amiram Eldar_, Feb 16 2020