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A000336 a(n) = a(n-1)*a(n-2)*a(n-3)*a(n-4); for n < 5, a(n) = n. 5

%I

%S 1,2,3,4,24,576,165888,9172942848,21035720123168587776,

%T 18437563379178327736384102280592359424,

%U 590180110002114158896983994712576414865667267958188575935810179040280576

%N a(n) = a(n-1)*a(n-2)*a(n-3)*a(n-4); for n < 5, a(n) = n.

%C The next term has 139 digits. - _Harvey P. Dale_, Jan 21 2019

%H T. D. Noe, <a href="/A000336/b000336.txt">Table of n, a(n) for n = 1..15</a>

%H B. K. Agarwala and F. C. Auluck, <a href="/A000093/a000093.pdf">Statistical mechanics and partitions into non-integral powers of integers</a>, Proc. Camb. Phil. Soc., 47 (1951), 207-216. [Annotated scanned copy]

%F a(n) = 2^A251656(n) * 3^A001631(n-1). - _Vaclav Kotesovec_, Feb 02 2016

%F a(n) = a(n-1)^2 / a(n-5), for n > 5. - _M. F. Hasler_, Apr 22 2018

%p A000336 := proc(n) option remember; if n <=4 then n else A000336(n-1)*A000336(n-2)*A000336(n-3)*A000336(n-4); fi; end;

%t t = {1, 2, 3, 4}; Do[AppendTo[t, t[[-1]]*t[[-2]]*t[[-3]]*t[[-4]]], {n, 5, 15}] (* _T. D. Noe_, Jun 19 2012 *)

%t nxt[{a_,b_,c_,d_}]:={b,c,d,a b c d}; NestList[nxt,{1,2,3,4},10][[All,1]] (* _Harvey P. Dale_, Jan 21 2019 *)

%o (PARI) a(n,a=[24,1,2,3,4])={for(n=6,n,a[n%5+1]=a[(n-1)%5+1]^2\a[n%5+1]);a[n%5+1]} \\ _M. F. Hasler_, Apr 22 2018

%o (PARI) first(n) = n = max(n, 5); my(res = vector(n)); for(i=1, 4, res[i] = i); res[5]=24; for(i = 6, n, res[i] = res[i-1]^2 / res[i - 5]); res \\ _David A. Corneth_, Apr 22 2018

%Y Cf. A000301, A000308, A001631, A003586, A251656.

%K nonn

%O 1,2

%A _N. J. A. Sloane_

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Last modified April 8 14:52 EDT 2020. Contains 333314 sequences. (Running on oeis4.)