Apologies if this is a repetition of earlier messages, which I've deleted, but I've just chanced upon Allan William Johnson, Problem 872, Prime magic squares, J. Recreational Math, 12:3(1980-81) 224 which gives 1255 as the smallest possible magic sum for a 5 x 5 symmetrical prime magic square 191 401 11 389 263 431 419 23 233 149 41 53 251 449 461 353 269 479 83 71 239 113 491 101 311 and 630 for a 6 x 6 such square 131 199 17 37 163 83 29 19 157 167 61 197 151 103 139 109 97 31 179 113 101 71 107 59 13 149 43 53 191 181 127 47 173 193 11 79 P.S. I've unsubscribed from the seqfan network -- if this was (also) on that, perhaps someone who's on both will forward it. Best to all, R.