OFFSET
1,2
COMMENTS
Conjecture: these numbers do not occur in A139491.
Complement sequence to A024352.
All odd numbers 2k+1 for k>0 can be represented by (k+1)^2-k^2. All multiples 4k for k>1 can be represented by (k+1)^2-(k-1)^2. No number of the form 4k+2 is the difference of two squares because, modulo 4, the differences of two squares are 0, 1, or 3. [T. D. Noe, Apr 27 2009]
A024359(a(n)) = 0. - Reinhard Zumkeller, Nov 09 2012
LINKS
MATHEMATICA
a[1] = 1; a[2] = 2; a[3] = 4; a[n_] := 4*n-10; Array[a, 60] (* Jean-François Alcover, May 27 2015 *)
PROG
(Haskell)
a139544 n = a139544_list !! (n-1)
a139544_list = 1 : 2 : 4 : tail a016825_list
-- Reinhard Zumkeller, Nov 09 2012
(PARI) is(n)=n%4==2||n==1||n==4 \\ Charles R Greathouse IV, May 31 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Artur Jasinski, Apr 25 2008
EXTENSIONS
Corrected by T. D. Noe, Apr 27 2009
STATUS
approved