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 A073473 Primes (including 1) forming 3 X 3 magic square with prime entries and minimal constant 111 = A073502(3). 3
 1, 7, 13, 31, 37, 43, 61, 67, 73 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Until the early part of the twentieth century 1 was regarded as a prime (cf. A008578). "The problem of constructing magic squares with prime numbers only was first discussed by myself in The Weekly Dispatch for Jul 22 1900 and Aug 05 1900; but during the last three or four years it has received great attention from American mathematicians. First, they have sought to form these squares with the smallest possible constants. "Thus the first nine prime numbers, 1 to 23 inclusive, sum to 99, which (being divisible by 3) is theoretically a suitable series; yet it has been demonstrated that the smallest possible constant is 111 and the required series as follows: 1,7,13,31,37,43,61,67,73." - Dudeney See A024351 for the "modern" version of the minimal 3 X 3 magic square of primes. - M. F. Hasler, Oct 30 2018 REFERENCES H. E. Dudeney, Amusements in Mathematics, Nelson, London, 1917, page 125. LINKS Harvey Heinz, Prime Magic Squares EXAMPLE The square is [ 43 1 67 / 61 37 13 / 7 73 31 ]. CROSSREFS Cf. A008578, A073350, A073502. Cf. A024351, A164843. Sequence in context: A063583 A065764 A273757 * A272407 A040084 A151723 Adjacent sequences:  A073470 A073471 A073472 * A073474 A073475 A073476 KEYWORD nonn,fini,full AUTHOR Lee Sallows (Sallows(AT)psych.kun.nl), Aug 27 2002 STATUS approved

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Last modified January 20 17:05 EST 2019. Contains 319335 sequences. (Running on oeis4.)