[seqfan] Re: computation for D4 lattice (A117216)

Richard Mathar mathar at strw.leidenuniv.nl
Thu Feb 4 12:17:32 CET 2010

```In reply to http://list.seqfan.eu/pipermail/seqfan/2010-February/003584.html :

This confirms a correction already submitted:

> Return-Path: <oeis at oeis.org>
> Date: Wed, 3 Feb 2010 13:42:14 -0500
> From: oeis at oeis.org
> Cc: mathar at strw.leidenuniv.nl
> Subject: COMMENT FROM submitA R. J. Mathar A117216
>
> This copy is just for your records.  No reply is expected.
>
> %S A117216 1,40,272,888,2080,4040,6960,11032,16448,23400,32080,42680,55392,70408,
> %T A117216 87920,108120
> %E A117216 a(2) corrected and sequence extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 03 2010
> %F A117216 Conjecture: a(n)= 4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4), n>4; a(n)= 8*n*(1+4*n^2), n>0 (bisection of A035878 and A105374). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 03 2010]
> %p A117216 A117216 := proc(n) a :=0 ; for x from -n to n do for y from -n to n do for z from -n to n do for w from -n to n do if type(x+y+z+w,'even') then m := max( abs(x),abs(y),abs(z),abs(w)) ; if m = n then a := a+1 ; end if; end if; end do ; end do ; end do ; end do ; a ; end proc: seq(A117216(n),n=0..15) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 03 2010]
>
>

```