A299399 a(n) = a(n-1)*a(n-2)*a(n-3)*a(n-4); a(0..3) = (1, 1, 2, 3).

1, 1, 2, 3, 6, 36, 1296, 839808, 235092492288, 9211413321697223245824, 2356948205087252000835395074931259831484416, 4286423488783965214900384842824017360544199884413056912194095171350270745233063936

Offset: 0

Author

M. F. Hasler, Apr 22 2018

Keywords

• nonn

Comments

A variant of A000336 which uses initial values (1,2,3,4).

A multiplicative variant of the tetranacci sequences A000078, A001631 and other variants.

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..14

Crossrefs

Cf. A000336 (variant starting 1,2,3,4).

Cf. A000301 (order 2 variant), A000308 (order 3 variant).

Subsequence of A003586 (3-smooth numbers).

Cf. A000078, A001631 (additive variants).

Programs

Mathematica

nxt[{a_,b_,c_,d_}]:={b,c,d,a b c d}; NestList[nxt,{1,1,2,3},13][[All,1]] (* Harvey P. Dale, Jun 09 2022 *)

PARI

A299399(n,a=[1,1,2,3,6])={for(n=5,n,a[n%#a+1]=a[(n-1)%#a+1]^2\a[n%#a+1]);a[n%#a+1]}

Formula

a(n) = a(n-1)^2 / a(n-5) for n > 4.

a(n) = 2^A001631(n)*3^A000078(n).