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

Author

N. J. A. Sloane, May 10 2015

Keywords

• nonn
• base

Comments

a(n) = 0 iff n is in A352535. - Bernard Schott, Jul 08 2022

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A257587, A257796.

Cf. A225693, A003132, A352535.

Programs

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

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

Mathematica

Array[Abs@ Total@ MapIndexed[(2 Boole@ EvenQ[First[#2]] - 1) (#1^2) &, IntegerDigits[#]] &, 70] (* Michael De Vlieger, Feb 27 2022 *)

PARI

a(n) = my(d=digits(n)); abs(sum(k=1, #d, (-1)^k*d[k]^2)); \\ Michel Marcus, Feb 27 2022

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