A257588 If n = abcd... in decimal, a(n) = |a^2 - b^2 + c^2 - d^2 + ...|.
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
Offset: 0
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
Programs
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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 -- Reinhard Zumkeller, May 10 2015
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Maple
a:= n-> (l-> abs(add(l[i]^2*(-1)^i, i=1..nops(l))))(convert(n, base, 10)): seq(a(n), n=0..70); # Alois P. Heinz, Mar 24 2022
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Mathematica
Array[Abs@ Total@ MapIndexed[(2 Boole@ EvenQ[First[#2]] - 1) (#1^2) &, IntegerDigits[#]] &, 70] (* Michael De Vlieger, Feb 27 2022 *)
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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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Python
def A257588(n): return abs(sum((int(d)**2*(-1)**j for j,d in enumerate(str(n))))) # Chai Wah Wu, May 10 2015
Comments