A280343 Number of 2 X 2 matrices with all elements in {-n,..,0,..,n} with determinant = 2*permanent.

1, 25, 81, 233, 401, 585, 1009, 1289, 1681, 2377, 2913, 3353, 4497, 5033, 5793, 7097, 8065, 8761, 10721, 11513, 12961, 14873, 16113, 17065, 19873, 21225, 22689, 25465, 27585, 28793, 32561, 33865, 36113, 39177, 41121, 43481, 48801, 50361, 52529, 56201, 59793

Offset

0,2

Links

Indranil Ghosh and Chai Wah Wu, Table of n, a(n) for n = 0..10000 (terms n = 0..145 from Indranil Ghosh)

Prog

(Python)
def t(n):
    s=0
    for a in range(-n, n+1):
        for b in range(-n, n+1):
            for c in range(-n, n+1):
                for d in range(-n, n+1):
                    if (a*d-b*c)==2*(a*d+b*c):
                        s+=1
    return s
for i in range(0, 146):
    print str(i)+" "+str(t(i))

Crossrefs

Cf. A016754 (Number of 2 X 2 matrices with all elements in {0,..,n} with determinant = 2* permanent).

Sequence in context: A251311 A223181 A016814 * A204708 A174623 A100487

Adjacent sequences: A280340 A280341 A280342 * A280344 A280345 A280346

Keyword

nonn

Author

Indranil Ghosh, Jan 01 2017

Status

approved