408201domain: NAppears in sequences"BGJ" (reversible, element, labeled) transform of 0,1,1,1...at n=13A032051Euler transform of sigma(n), cf. A000203.at n=20A061256Number of (n+1)X(n+1) -11..11 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.at n=9A211714