Problem 44341. Hexagonal numbers on a spiral matrix
Put hexagonal numbers in a ( m x m ) spiral matrix and return the sum of its diagonal elements.
Formula of hexagonal numbers h(n) = 2n^2 - n
If m = 5;
spiral(5) = 21 22 23 24 25 20 7 8 9 10 19 6 1 2 11 18 5 4 3 12 17 16 15 14 13
First 5x5=25 hexagonal numbers are;
h = [1 6 15 28 45 66 91 120 153 190 231 276 325 378 435 496 561 630 703 780 861 946 1035 1128 1225]
We put them in a spiral format;
spiralHex = [ 861 946 1035 1128 1225 780 91 120 153 190 703 66 1 6 231 630 45 28 15 276 561 496 435 378 325
And sum its diag = 861 + 91 + 1 + 15 + 325 = 1293.
Return the output as char.
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