A374854 a(n) = (1/30)*A028361(n) for n>=3.

1, 9, 153, 5049, 328185, 42335865, 10880317305, 5581602777465, 5721142846901625, 11722621693301429625, 48027581077455957173625, 393489971767596657123509625, 6447333187412071226968705205625, 211272661218306162036537500883125625

Offset: 3

Author

Clark Kimberling, Aug 05 2024

Keywords

• nonn

Comments

a(n+1)/a(n) is an integer for n>=0, so (a(n)) is a divisibility sequence.

Crossrefs

Cf. A000012, A000079, A060202, A374848.

Programs

Mathematica

s[n_] := 1; t[n_] := 2^n;
u[n_] := Product[s[k] + t[n - k], {k, 0, n}]
(1/30) Table[u[n], {n, 2, 20}]

Formula

a(n) = (1/30)(s**t)(n), where s = A000012 = (1,1,1,...), t = A000079 = (1,2,4,8,16,...), and ** denotes obverse convolution, as in A374848.

a(n) = A060202(n+1)/180. - Hugo Pfoertner, Aug 07 2024