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A061873
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Numbers n such that |first digit - second digit + third digit - fourth digit ...| = 4.
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1
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4, 15, 26, 37, 40, 48, 51, 59, 62, 73, 84, 95, 103, 114, 125, 136, 147, 150, 158, 161, 169, 172, 183, 194, 202, 213, 224, 235, 246, 257, 260, 268, 271, 279, 282, 293, 301, 312, 323, 334, 345, 356, 367, 370, 378, 381, 389, 392, 400, 411, 422, 433, 444, 455
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listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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LINKS
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MAPLE
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F:= proc(n) option remember;
-procname(floor(n/10)) + (n mod 10)
end proc:
for j from 0 to 9 do F(j):= j od:
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MATHEMATICA
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Do[ a = IntegerDigits[ n ]; l = Length[ a ]; e = o = {}; Do[ o = Append[ o, a[ [ 2k - 1 ] ] ], {k, 1, l/2 + .5} ]; Do[ e = Append[ e, a[ [ 2k ] ] ], {k, 1, l/2} ]; If[ Abs[ Apply[ Plus, o ] - Apply[ Plus, e ] ] == 4, Print[ n ] ], {n, 1, 1000} ]
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PROG
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(Python)
def ok(n): return abs(sum((-1)**i*int(d) for i, d in enumerate(str(n))))==4
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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