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A257588 If n = abcd... in decimal, a(n) = |a^2 - b^2 + c^2 - d^2 + ...|. 8
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

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

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 *)

PROG

(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

(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

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

CROSSREFS

Cf. A257587, A257796.

Cf. A225693, A003132, A352535.

Sequence in context: A098736 A002015 A257587 * A352598 A303269 A003132

Adjacent sequences: A257585 A257586 A257587 * A257589 A257590 A257591

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, May 10 2015

STATUS

approved

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Last modified December 2 18:40 EST 2022. Contains 358510 sequences. (Running on oeis4.)