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 A225371 a(n) = number of squares in M(n,2), the ring of n X n matrices over GF(2). 5
 1, 2, 10, 260, 31096, 13711952, 28275659056, 224402782202048, 7293836994286696576, 952002419516769475035392, 497678654312172407869125822976, 1044660329769242614113093804053562368, 8745525723307044762290950664928498588583936 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(0)-a(4) computed by W. Edwin Clark, May 07 2013. A226321 is a similar sequence which counts the real {0,1} matrices which are the square of a {0,1} matrix. - Giovanni Resta, Jun 03 2013 LINKS Victor S. Miller, Table of n, a(n) for n = 0..30 Victor S. Miller, Counting Matrices that are Squares, arXiv:1606.09299 [math.GR], 2016. Giovanni Resta, C program for a(k), with k <= 6. PROG (PARI) a(n)=#vecsort(lift(vector(2^n^2, k, matrix(n, n, i, j, bittest(k, (i-1)*n+j-1))^2*Mod(1, 2))), , 8) \\ Charles R Greathouse IV, May 07 2013 (PARI) ZM(k)=matrix(n, n, i, j, bittest(k, (i-1)*n+j-1))*Mod(1, 2) MZ(M)=my(n=matsize(M)); sum(i=1, n, sum(j=1, n, M[i, j]<<((i-1)*n+j-1))) a(n)=#vecsort(vector(2^n^2, i, MZ(lift(ZM(i, n)^2))), , 8) \\ Charles R Greathouse IV, May 07 2013 CROSSREFS Cf. A226321, A121231, A266462, A274313. Sequence in context: A289948 A282567 A308756 * A088310 A134473 A005154 Adjacent sequences:  A225368 A225369 A225370 * A225372 A225373 A225374 KEYWORD nonn,hard AUTHOR N. J. A. Sloane, May 07 2013 EXTENSIONS a(5)-a(6) from Giovanni Resta, May 08 2013 a(7)-a(30) from Victor S. Miller, May 24 2013 STATUS approved

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Last modified October 26 21:33 EDT 2021. Contains 348269 sequences. (Running on oeis4.)