OFFSET
1,2
COMMENTS
Dirichlet convolution of [1,0,0,3,0,0,0,2,0,0,...] with A007425. - R. J. Mathar, Sep 25 2017
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
J. S. Rutherford, The enumeration and symmetry-significant properties of derivative lattices, Acta Cryst. A48 (1992), 500-508. See Table 1, symmetry Cmmm.
FORMULA
From Amiram Eldar, Oct 25 2022: (Start):
Multiplicative with a(2^e) = 3*(e-1)*e+3 for e > 0, and a(p^e) = (e+1)*(e+2)/2 if p > 2.
MAPLE
nmax := 10000 :
L := [1, 0, 0, 3, 0, 0, 0, 2, seq(0, i=1..nmax)] :
MOBIUSi(%) :
MOBIUSi(%) :
MOBIUSi(%) ; # R. J. Mathar, Sep 25 2017
MATHEMATICA
f[p_, e_] := (e + 1)*(e + 2)/2; f[2, e_] := 3*(e - 1)*e + 3; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Oct 25 2022 *)
PROG
(PARI) t1=direuler(p=2, 200, 1/(1-X)^3)
t2=direuler(p=2, 2, 1+3*X^2+2*X^3, 200)
t3=dirmul(t1, t2)
(PARI) a(n) = {my(f = factor(n)); prod(i = 1, #f~, if(f[i, 1] == 2, 3*(f[i, 2]-1)*f[i, 2]+3, (f[i, 2]+1)*(f[i, 2]+2)/2)); } \\ Amiram Eldar, Oct 25 2022
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
N. J. A. Sloane, Mar 14 2009
STATUS
approved