%I #10 Feb 11 2025 14:33:28

%S 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,3,1,1,1,1,1,1,1,1,1,1,1,1,

%T 1,1,1,1,1,1,1,1,1,1,1,1,1,3,1,3,1,1,1,1,3,1,1,1,1,1,1,1,1,1,1,1,1,1,

%U 1,1,1,3,1,1,1,1,1,1,5,1,1,1,1,1,5,3,1

%N Class number of real quadratic field Q(sqrt(prime(n))).

%C A278837 contains all primes p where the class number of Q(sqrt(p)) is larger than 1.

%e For n = 22, a(22) = 3 since the class number of Q(sqrt(79)) is 3 where 79 is the 22nd prime.

%t Table[NumberFieldClassNumber[Sqrt[Prime[i]]], {i, 87}]

%Y Cf. A003172, A076498, A278837.

%K nonn

%O 1,22

%A _Steven Lu_, Feb 02 2025