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 A109056 To compute a(n) we first write down 4^n 1's in a row. Each row takes the rightmost 4th part of the previous row and each element in it equals sum of the elements of the previous row starting with the first of the rightmost 4th part. The single element in the last row is a(n). 7

%I

%S 1,1,4,58,3236,713727,627642640,2205897096672,31004442653082720,

%T 1743005531132374350208

%N To compute a(n) we first write down 4^n 1's in a row. Each row takes the rightmost 4th part of the previous row and each element in it equals sum of the elements of the previous row starting with the first of the rightmost 4th part. The single element in the last row is a(n).

%e For example, for n=3 the array looks like this:

%e 1..1.....1..1..1..1..1..1..1..1..1..1..1..1..1..1..1..1..1

%e ............1..2..3..4..5..6..7..8..9.10.11.12.13.14.15.16

%e ...............................................13.27.42.58

%e ........................................................58

%e Therefore a(4)=58.

%p proc(n::nonnegint) local f,a; if n=0 or n=1 then return 1; end if; f:=L->[seq(add(L[i],i=3*nops(L)/4+1..j),j=3*nops(L)/4+1..nops(L))]; a:=f([seq(1,j=1..4^n)]); while nops(a)>4 do a:=f(a) end do; a[4]; end proc;

%K nonn

%O 0,3

%A _Augustine O. Munagi_, Jun 17 2005

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Last modified May 28 02:19 EDT 2020. Contains 334671 sequences. (Running on oeis4.)