A048572 - OEIS

%I #20 Dec 14 2023 05:22:05

%S 1,2,2,4,8,5,4,2,8,7,11,14,10,5,5,7,8,11,16,14,8,4,5,2,1,2,2,4,8,5,4,

%T 2,8,7,11,14,10,5,5,7,8,11,16,14,8,4,5,2,1,2,2,4,8,5,4,2,8,7,11,14,10,

%U 5,5,7,8,11,16,14,8,4,5,2

%N a(n) = sum of digits of a(n-1)*a(n-2).

%C This sequence is periodic with period 24. - _T. D. Noe_, Feb 15 2008

%H <a href="/index/Rec#order_24">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).

%F a(n) = a(n-24) for n >= 25. - _Wesley Ivan Hurt_, Mar 09 2023

%t Nest[Append[#,Total[IntegerDigits[Last[#]#[[-2]]]]]&,{1,2},80]  (* _Harvey P. Dale_, Apr 21 2011 *)

%t PadRight[{},100,{1,2,2,4,8,5,4,2,8,7,11,14,10,5,5,7,8,11,16,14,8,4,5,2}] (* _Harvey P. Dale_, Jan 18 2015 *)

%K nonn,easy,nice,base

%O 1,2

%A _David Johnson-Davies_