A390526 - OEIS

%I #18 Dec 27 2025 15:35:04

%S 4,6,9,10,15,25,26,31,39,41,49,65,71,74,79,86,89,106,111,121,129,134,

%T 151,159,166,169,185,191,199,201,214,215,239,241,249,265,271,281,289,

%U 311,314,321,326,335,346,359,361,394,401,409,415,431,439,449,454,471,479,481,489

%N Norms of irreducible elements of Z[sqrt(10)].

%C Note that Q(sqrt(10)) has class number 2.

%C A391362 is the main sequence.

%H Jianing Song, <a href="/A390526/b390526.txt">Table of n, a(n) for n = 1..10000</a>

%Y Cf. A097955 (primes decomposing in Q(sqrt(10))), A038880 (primes remaining inert in Q(sqrt(10))), A141180 ((p) is the product of two principal ideals), A141179 ((p) is the product of two non-principal ideals).

%Y Other sequences related to factorizations in Z[sqrt(10)]: A391367, A391362, A262362.

%Y Analogs in other quadratic fields with class number 2: A390422 (discriminant -15), A091730 (discriminant -20), A390498 (discriminant -24).

%K nonn,easy

%O 1,1

%A _Jianing Song_, Dec 07 2025