1,4

a(4) computed by Frenicle de Bessy in 1693.

a(5) computed by Richard Schroeppel in 1973.

According to Pinn and Wieczerkowski, a(6) = (0.17745 +- 0.00016) * 10^20. - R. K. Guy, May 01, 2004.

E. R. Berlekamp, J. H. Conway and R. K. Guy, Winning Ways, Vol. II, pp. 778-783 gives the 880 4 X 4 squares.

M. Gardner, Mathematical Games, Sci. Amer. Vol. 249 (No. 1, 1976), p. 118.

M. Gardner, Time Travel and Other Mathematical Bewilderments. Freeman, NY, 1988, p. 216.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

I. Peterson, Magic Tesseracts

K. Pinn and C. Wieczerkowski, Number of magic squares from parallel tempering Monte Carlo, Internat. J. Modern Phys., 9 (4) (1998) 541-546.

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Index entries for sequences related to magic squares

An illustration of the unique square of order 3:

|---+---+---|

| 2 | 7 | 6 |

|---+---+---|

| 9 | 5 | 1 |

|---+---+---|

| 4 | 3 | 8 |

|---+---+---|

Sequence in context: A063051 A118799 A024393 this_sequence A105976 A137064 A092675

Adjacent sequences: A006049 A006050 A006051 this_sequence A006053 A006054 A006055

nonn,hard,nice,more

N. J. A. Sloane (njas(AT)research.att.com).