Magic constant
A magic square is a square grid containing consecutive integers from 1 to N², arranged so that every row, column and diagonal adds up to the same number. That number is a constant. There is no way to create a valid N x N magic square that does not sum to the associated constant.
- EG
A 3 x 3 magic square always sums to 15.
┌───┬───┬───┐
│ 2 │ 7 │ 6 │
├───┼───┼───┤
│ 9 │ 5 │ 1 │
├───┼───┼───┤
│ 4 │ 3 │ 8 │
└───┴───┴───┘
A 4 x 4 magic square always sums to 34.
Traditionally, the sequence leaves off terms for n = 0 and n = 1 as the magic squares of order 0 and 1 are trivial; and a term for n = 2 because it is impossible to form a magic square of order 2.
- Task
- Starting at order 3, show the first 20 magic constants.
- Show the 1000th magic constant. (Order 1003)
- Find and show the order of the smallest N x N magic square whose constant is greater than 10¹ through 10¹⁰.
- Stretch
- Find and show the order of the smallest N x N magic square whose constant is greater than 10¹¹ through 10²⁰.
- See also
- Wikipedia: Magic constant
- OEIS: A006003 (Similar sequence, though it includes terns for 0, 1 & 2.)
Raku
<lang perl6>use Lingua::EN::Numbers:ver<2.8+>;
my @magic-constants = lazy (3..∞).hyper.map: { (1 + .²) * $_ / 2 };
put "First 20 magic constants: ", @magic-constants[^20]»., say "1000th magic constant: ", @magic-constants[999]., say "\nSmallest order magic square with a constant greater than:";
(1..20).map: -> $p {printf "10%-2s: %s\n", $p.&super, comma 3 + @magic-constants.first( * > exp($p, 10), :k ) }</lang>
- Output:
First 20 magic constants: 15 34 65 111 175 260 369 505 671 870 1,105 1,379 1,695 2,056 2,465 2,925 3,439 4,010 4,641 5,335 1000th magic constant: 503,006,505 Smallest order magic square with a constant greater than: 10¹ : 3 10² : 6 10³ : 13 10⁴ : 28 10⁵ : 59 10⁶ : 126 10⁷ : 272 10⁸ : 585 10⁹ : 1,260 10¹⁰: 2,715 10¹¹: 5,849 10¹²: 12,600 10¹³: 27,145 10¹⁴: 58,481 10¹⁵: 125,993 10¹⁶: 271,442 10¹⁷: 584,804 10¹⁸: 1,259,922 10¹⁹: 2,714,418 10²⁰: 5,848,036