# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/
Search: id:a320873
Showing 1-1 of 1
%I A320873 #29 Apr 17 2022 03:54:32
%S A320873 1480028141,1480028189,1480028183,1480028213,1480028171,1480028129,
%T A320873 1480028159,1480028153,1480028201,1850590069,1850590117,1850590111,
%U A320873 1850590141,1850590099,1850590057,1850590087,1850590081,1850590129,5196185959,5196186007,5196186001,5196186031,5196185989,5196185947,5196185977,5196185971,5196186019
%N A320873 List of 3 X 3 magic squares made of consecutive primes, in order of increasing magic sum. Only the lexicographically smallest variant of equivalent squares (modulo D4 symmetries) is listed, as a row containing the 3 rows of the square.
%C A320873 The first row is the lexicographically first 3 X 3 magic square of consecutive primes with the smallest possible magic constant 4440084513 = A270305(1) = A073520(3).
%C A320873 The same 9 terms are also given in increasing order in sequence A073519. But this is equivalent of giving just the smallest of the terms (cf. A256891) or the central element (cf. A166113) or the magic constant itself (cf. A270305), which uniquely determines the sequence of primes since they have to be consecutive and their sum is equal to 3 times the magic constant.
%C A320873 In the case of 3 X 3 magic squares, however, the lexicographically smallest representative has its elements in a well-defined order, see comment in A320872. This allows the reconstruction of the square from the set of primes which can be computed from the central elements A166113 or magic constants A270305, cf. PROGRAM in A073519.
%D A320873 Allan W. Johnson, Jr., Journal of Recreational Mathematics, vol. 23:3, 1991, pp. 190-191.
%D A320873 Clifford A. Pickover, The Zen of Magic Squares, Circles and Stars: An Exhibition of Surprising Structures across Dimensions, Princeton University Press, 2002.
%H A320873 Harvey Heinz, Prime Magic Squares
%H A320873 Index entries for sequences related to magic squares
%F A320873 a(9n-4) = A166113(n) = A270305(n)/3 for all n >= 1.
%e A320873 The first row of 9 terms, (1480028141, 1480028189, 1480028183, 1480028213, 1480028171, 1480028129, 1480028159, 1480028153, 1480028201), corresponds to the following smallest 3 X 3 magic square of consecutive primes:
%e A320873 [1480028141 1480028189 1480028183]
%e A320873 [1480028213 1480028171 1480028129] .
%e A320873 [1480028159 1480028153 1480028201]
%e A320873 The eleventh row yields the first example where the second term is smaller than the third one:
%e A320873 [23813359643 23813359721 23813359727]
%e A320873 [23813359781 23813359697 23813359613] .
%e A320873 [23813359667 23813359673 23813359751]
%o A320873 (PARI) A320873_row(n)=vecextract(n=MagicPrimes(3*A166113[n],3),[2,6+n=n[2]*2==n[1]+n[3],7-n,9,5,1,3+n,4-n,8]) \\ For MagicPrimes() see A073519 (the set of primes of the first row).
%o A320873 /* the following allows the production of all 8 variants of a magic square that are equivalent modulo reflection on any of the 4 symmetry axes of the square */
%o A320873 REV(M)=matconcat(Vecrev(M)) \\ reverse the order of columns of M
%o A320873 FLIP(M)=matconcat(Colrev(M)) \\ reverse the order of rows of M
%o A320873 ALL(M,C(f,L)=concat(apply(f,L),L))=Set(C(REV,C(FLIP,[M,M~]))) \\ PARI orders the set according to the (first) columns of the matrices, so one must take the transpose to get them ordered according to elements of the first row.
%Y A320873 Cf. A073519, A073520, A073521, A073522.
%Y A320873 Cf. A073520 (smallest magic sum for a n X n magic square made from consecutive primes).
%Y A320873 Cf. A104157 (smallest of n^2 consecutive primes forming a magic square).
%Y A320873 Cf. A166113 (center element of 3 X 3 magic squares of consecutive primes).
%Y A320873 Cf. A256891 (smallest entry of 3 X 3 magic squares of consecutive primes) = A151799^4(A166113).
%Y A320873 Cf. A270305 (magic sums of 3 X 3 magic squares of consecutive primes) = 3*A166113.
%K A320873 nonn,tabf
%O A320873 1,1
%A A320873 _M. F. Hasler_, Oct 22 2018
# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE