A135462 a(n) = number of Eisenstein primes (see A055664) of norm <= n.

0, 0, 0, 6, 12, 12, 12, 24, 24, 24, 24, 24, 24, 36, 36, 36, 36, 36, 36, 48, 48, 48, 48, 48, 48, 54, 54, 54, 54, 54, 54, 66, 66, 66, 66, 66, 66, 78, 78, 78, 78, 78, 78, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 102, 102, 102, 102, 102

Offset: 0

Author

N. J. A. Sloane, Feb 06 2008

Keywords

• nonn

References

• L. W. Reid, The Elements of the Theory of Algebraic Numbers, MacMillan, NY, 1910, see Chap. VI.

Crossrefs

Cf. A135461, A055664, A055667.

Programs

Mathematica

A055667[n_] := Which[n == 3, 6, PrimeQ[n] && Mod[n, 6] == 1, 12, PrimeQ[p = Sqrt[n]] && Mod[p, 3] == 2, 6, True, 0]; Accumulate[Array[A055667, 66, 0]] (* Jean-François Alcover, Feb 28 2018 *)

Formula

a(n) = a(n-1) + A055667(n) for n > 0. - Seiichi Manyama, Dec 09 2017

Extensions

Terms corrected by Seiichi Manyama, Dec 09 2017