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A257588
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If n = abcd... in decimal, a(n) = |a^2 - b^2 + c^2 - d^2 + ...|.
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8
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0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 1, 0, 3, 8, 15, 24, 35, 48, 63, 80, 4, 3, 0, 5, 12, 21, 32, 45, 60, 77, 9, 8, 5, 0, 7, 16, 27, 40, 55, 72, 16, 15, 12, 7, 0, 9, 20, 33, 48, 65, 25, 24, 21, 16, 9, 0, 11, 24, 39, 56, 36, 35, 32, 27, 20, 11, 0, 13, 28, 45, 49
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OFFSET
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0,3
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COMMENTS
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LINKS
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MAPLE
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a:= n-> (l-> abs(add(l[i]^2*(-1)^i, i=1..nops(l))))(convert(n, base, 10)):
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MATHEMATICA
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Array[Abs@ Total@ MapIndexed[(2 Boole@ EvenQ[First[#2]] - 1) (#1^2) &, IntegerDigits[#]] &, 70] (* Michael De Vlieger, Feb 27 2022 *)
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PROG
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(Haskell)
a257588 = abs . f 1 where
f _ 0 = 0
f s x = s * d ^ 2 + f (negate s) x' where (x', d) = divMod x 10
(Python)
return abs(sum((int(d)**2*(-1)**j for j, d in enumerate(str(n)))))
(PARI) a(n) = my(d=digits(n)); abs(sum(k=1, #d, (-1)^k*d[k]^2)); \\ Michel Marcus, Feb 27 2022
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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