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A175499 a(n) = A175498(n+1)-A175498(n). 7
1, 2, -1, 3, 4, -5, 6, -4, 5, -3, 7, -8, 9, -2, 8, -10, 11, -6, 10, -14, 12, -7, 13, -12, 14, -13, 15, -11, 16, -19, 17, -9, 18, -21, 19, -17, 20, -18, 21, -15, 22, -26, 23, -16, 24, -29, 25, -22, 27, -23, 26, -25, 28, -27, 29, -28, 30, -24, 31, -35, 32, 33, -62, 34, -31, 35, -34, 36, -33, 37, -39, 38, -32, 39, -42, 40, -36 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

No integer occurs in this sequence more than once, by definition. Is this sequence a permutation of the nonzero integers?

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..4999

MATHEMATICA

a[1] = 0; d[1] = 1; k = 1; z = 10000; zz = 120;

A[k_] := Table[a[i], {i, 1, k}]; diff[k_] := Table[d[i], {i, 1, k}];

c[k_] := Complement[Range[-z, z], diff[k]];

T[k_] := -a[k] + Complement[Range[z], A[k]]

Table[{h = Min[Intersection[c[k], T[k]]], a[k + 1] = a[k] + h,

   d[k + 1] = h, k = k + 1}, {i, 1, zz}];

u = Table[a[k], {k, 1, zz}]  (* A257884 *)

Table[d[k], {k, 1, zz}] (* A175499 *)

(* Clark Kimberling, May 13 2015 *)

PROG

(Python)

A175499_list, l, s, b = [1], 2, 3, set()

for n in range(2, 10**2):

....i, j = s, s-l

....while True:

........if not (i in b or j in A175499_list):

............A175499_list.append(j)

............b.add(i)

............l = i

............while s in b:

................b.remove(s)

................s += 1

............break

........i += 1

........j += 1 # Chai Wah Wu, Dec 15 2014

(Haskell)

a175499 n = a175499_list !! (n-1)

a175499_list = zipWith (-) (tail a175498_list) a175498_list

-- Reinhard Zumkeller, Apr 25 2015

CROSSREFS

Cf. A175498, A257884, A131389.

Sequence in context: A169808 A283069 A304528 * A181440 A035043 A288118

Adjacent sequences:  A175496 A175497 A175498 * A175500 A175501 A175502

KEYWORD

sign

AUTHOR

Leroy Quet, May 31 2010

EXTENSIONS

More terms from Sean A. Irvine, Jan 27 2011

STATUS

approved

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Last modified December 10 20:55 EST 2018. Contains 318049 sequences. (Running on oeis4.)