[seqfan] useful complifification in A130102?
Rainer Rosenthal
r.rosenthal at web.de
Sun Feb 14 15:48:42 CET 2010
in http://www.research.att.com/~njas/sequences/A130102
we learn:
a(n)=2^n-2n+2*C(2, n)-4*C(1, n)+2*C(0, n);
The essence of that is:
a(2) = 2, a(n) = 2^n - 2n for n /= 2
since we can write a(n) = 2^n - 2n + Z(n) where Z(n) is given by the
following little table:
:
: n C(0,n) C(1,n) C(2,n) Z(n)
: ------------------------------------------------------------------
: 0 1 1 1 2*1 - 4*1 + 2*1 = 0
: 1 0 1 2 2*0 - 4*1 + 2*2 = 0
: 2 0 0 1 2*0 - 4*0 + 2*1 = 2
: 3 etc. 0 0 0 2*0 - 4*0 + 2*0 = 0
:____________________________________________________________________
:
: Table 1: function Z(n) demasked
:
Is there any value in having such a complicated expression here?
Cheers,
Rainer
More information about the SeqFan
mailing list