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

0,3

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

Formula

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

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

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 *)

Prog

(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]}

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).

Sequence in context: A351883 A129379 A000308 * A173501 A018340 A299121

Adjacent sequences: A299396 A299397 A299398 * A299400 A299401 A299402

Keyword

nonn

Author

M. F. Hasler, Apr 22 2018

Status

approved