|
|
A307967
|
|
G.f. A(x) satisfies: A(x) = x + x^2 + x^3 * (1 + Sum_{i>=1} Sum_{j>=1} A(x^(i*j))).
|
|
2
|
|
|
1, 1, 1, 1, 3, 3, 6, 5, 11, 8, 14, 16, 20, 16, 37, 22, 34, 49, 44, 36, 90, 46, 73, 108, 80, 75, 181, 89, 121, 210, 151, 123, 334, 153, 197, 368, 227, 219, 567, 229, 313, 613, 365, 315, 871, 367, 461, 986, 519, 463, 1355, 534, 660, 1429, 756, 662, 1960, 794, 940, 2054
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,5
|
|
COMMENTS
|
Shifts 3 places left when inverse Moebius transform applied twice.
|
|
LINKS
|
|
|
FORMULA
|
a(1) = a(2) = a(3) = 1; a(n+3) = Sum_{d|n} tau(n/d)*a(d), where tau = number of divisors (A000005).
|
|
MATHEMATICA
|
a[n_] := a[n] = Sum[DivisorSigma[0, (n - 3)/d] a[d], {d, Divisors[n - 3]}]; a[1] = a[2] = a[3] = 1; Table[a[n], {n, 1, 60}]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|