cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A024351 Primes forming a 3 X 3 magic square with prime entries and minimal constant 177 = A164843(3).

Original entry on oeis.org

5, 17, 29, 47, 59, 71, 89, 101, 113
Offset: 1

Views

Author

Karl Schmerbauch (karl.j.schmerbauch(AT)boeing.com)

Keywords

Comments

The minimal 3 X 3 magic square made of consecutive primes has constant 4440084513 = A073520(3) = A270305(1), cf. A073519. - M. F. Hasler, Oct 22 2018
Sequence A073473 gives a variant using "primes including 1" (for historical reasons), to which also refers A073502. - M. F. Hasler, Oct 24 2018

Examples

			The square is [101 5 71 ; 29 59 89 ; 47 113 17].
The lexicographically smallest equivalent variant (modulo reflections on the symmetry axes of the square) is [17 89 71 ; 113 59 5 ; 47 29 101], cf. A320872. - _M. F. Hasler_, Oct 24 2018
		

Crossrefs

Cf. A320872 (3 X 3 magic squares of primes), A268790 (magic sums of these).

Programs

  • PARI
    A024351=select(p->setsearch(P,118-p),P=primes(30)[^5]) \\ 118 = 2*59, where 59 is the central prime; primes(30) = primes < 118. For the magic square itself, use A320872_row(1). -  M. F. Hasler, Oct 25 2018

Extensions

Offset corrected by Arkadiusz Wesolowski, Nov 26 2011

A073502 The smallest magic constant for n X n magic square with prime entries (regarding 1 as a prime).

Original entry on oeis.org

111, 102, 213, 408, 699, 1114, 1681, 2416, 3355, 4514, 5937, 7626, 9635, 11986, 14691, 17818, 21373, 25394, 29873, 34926, 40511, 46664, 53445, 60898, 69045, 77888, 87473, 97850, 109065, 121126, 134113, 147982, 162759
Offset: 3

Views

Author

N. J. A. Sloane, Aug 27 2002

Keywords

Comments

Until the early part of the twentieth century 1 was regarded as a prime (see A008578).

References

  • W. S. Andrews and H. A. Sayles, The Monist (Chicago) for October 1913.
  • H. E. Dudeney, Amusements in Mathematics, Nelson, London, 1917, page 125, who quotes the Andrews-Sayles article as his source.

Crossrefs

Cf. A073473 (for the n=3 square), A024351, A073520, A164843, A173079.

Extensions

Dudeney gives 36095/11 for n = 11 (an obvious typo) and 4514 for n = 12
a(3)-a(12) are confirmed/given by Chebrakov
a(15), a(17), a(22), a(35), and a(124)=9912840 from S. Tognon (cf. A173079)
a(13)-a(14), a(16), a(18)-a(21), a(23)-a(34) from N. Makarova
Edited by Max Alekseyev, Feb 11 2010

A073350 Primes not at the center of a 3 X 3 magic square of primes.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 61, 67, 79, 83, 97, 101, 107, 113, 163, 181, 197, 199, 223, 229, 233, 277, 313, 317, 331, 433, 439, 457, 569, 859
Offset: 1

Views

Author

David W. Wilson, Aug 25 2002

Keywords

Comments

The "magic sum" is always thrice the central entry.
There are no other terms < 5000.
There are no other terms < 100000. - Robert Israel, Feb 16 2016

Crossrefs

Cf. A073473. A magic square with 59 at center is given in A024351.

Programs

  • Maple
    N:= 10000: # to get all terms <= N
    P:= select(isprime,{seq(p,p=3..2*N,2)}):
    count:= 1:
    A[count]:= 2:
    for ic from 1 while P[ic] <= N do
       c:= P[ic];
       V:= map(`-`,P[ic+1..-1],c) intersect map(t -> c-t, P[1..ic-1]);
       nv:= nops(V);
       VV:= {seq(seq(V[j]-V[i],j=i+1..nv),i=1..nv-1)} intersect V;
       nvv:= nops(VV);
       found:= false;
       for ia from 1 to nvv while not found do
         a:= VV[ia];
         for ib from ia+1 to nvv while VV[ib] < c - a do
           b:= VV[ib];
           if b <> 2*a and {c-a-b,c-a+b,c-b+a,c+a+b} subset P then
              found:= true;
              break
           fi
         od
       od:
       if not found then
         count:= count+1;
         A[count]:= c;
       fi
    od:
    seq(A[i],i=1..count); # Robert Israel, Feb 16 2016
Showing 1-3 of 3 results.