|
%I #23 Jun 09 2022 18:31:22
%S 1,1,2,3,6,36,1296,839808,235092492288,9211413321697223245824,
%T 2356948205087252000835395074931259831484416,
%U 4286423488783965214900384842824017360544199884413056912194095171350270745233063936
%N a(n) = a(n-1)*a(n-2)*a(n-3)*a(n-4); a(0..3) = (1, 1, 2, 3).
%C A variant of A000336 which uses initial values (1,2,3,4).
%C A multiplicative variant of the tetranacci sequences A000078, A001631 and other variants.
%H Seiichi Manyama, <a href="/A299399/b299399.txt">Table of n, a(n) for n = 0..14</a>
%F a(n) = a(n-1)^2 / a(n-5) for n > 4.
%F a(n) = 2^A001631(n)*3^A000078(n).
%t 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 *)
%o (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]}
%Y Cf. A000336 (variant starting 1,2,3,4).
%Y Cf. A000301 (order 2 variant), A000308 (order 3 variant).
%Y Subsequence of A003586 (3-smooth numbers).
%Y Cf. A000078, A001631 (additive variants).
%K nonn
%O 0,3
%A _M. F. Hasler_, Apr 22 2018
|
