Note 'Lucky spiral'
http://en.wikipedia.org/wiki/Lucky_number
http://oeis.org/A000959
Seeing that lucky numbers have great commonality with
primes, I found that the lucky correspondent to Ulam spiral
shares diagonal lines.
)
lucky =: 3 : 0 NB. make lucky numbers from 1 to doubled y
A =. >: +: i. y
N =. 1
M =. 1
while. M (< #) A do.
M =. N { A
A =. ((#A) $ -. (-M) {. 1) # A
N =. >: N
end.
A
)
assert 1 3 7 9 13 15 21 25 -: lucky 13
cw=:|:@:|. NB. clockwise matrix rotation
assert (> 3 0 ; 4 1 ; 5 2) -: cw i. 2 3
spiral =: (, (>:@:(*/) + i.@:}.)@:$)@:cw
assert (> 5 4 3 ; 6 1 2 ; 7 8 9) -: (spiral^:4)1 1$1
L =: lucky 10000
S =: (spiral^:284) 1 1 $ 1
LS =: S e. L
ULAM =: 1 p: S
load'viewmat'
viewmat LS
NB. viewmat ULAM
NB. viewmat ULAM++:LS
NB. ps. lucky might be a good candidate as example
NB. for conversion to tacit form.
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