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URL: https://oeis.org/A284606

⇱ A284606 - OEIS

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A284606
a(n) = (-1)^n * A284019(n).
2
0, 0, 0, -1, 0, 0, 1, -1, 1, 0, -1, -1, 0, 0, 2, -1, 1, -1, 0, 0, 0, 1, -2, -2, -1, 1, 1, 0, 0, 0, 4, -1, 0, -2, 2, 1, -1, -1, -1, 1, -1, 1, -1, 2, -2, 3, -3, -5, -4, 4, 1, 2, -4, 0, -1, 3, 1, 1, 0, 0, 0, 0, 8, -1, -2, -4, 0, 3, 2, -2, -1, 1, 0, 2, -2, 3, -1, 4, -4
OFFSET
1,15
FORMULA
a(n) = (-1)^n * (A004001(n) - A005185(n)).
EXAMPLE
a(4) = -1 since a(4) = (-1)^4 * (A004001(4) - A005185(4)) = 2 - 3 = -1
MAPLE
A005185:= proc(n) option remember; procname(n-procname(n-1)) +procname(n-procname(n-2)) end proc:
A005185(1):= 1: A005185(2):= 1:
A004001:= proc(n) option remember; procname(procname(n-1)) +procname(n-procname(n-1)) end proc:
A004001(1):= 1: A004001(2):= 1:
A284606:= map((-1)^i * (A004001 - A005185), [$1..1000]):
seq(A284606[i], i=1..1000); # Altug Alkan, Apr 01 2017
MATHEMATICA
a[n_] := a[n] = If[n <= 2, 1, a[a[n - 1]] + a[n - a[n - 1]]]; b[1] = b[2] = 1; b[n_] := b[n] = b[n - b[n - 1]] + b[n - b[n - 2]]; Table[(-1)^n*(a@ n - b@ n), {n, 87}] (* Michael De Vlieger, Apr 02 2017, after Robert G. Wilson v at A004001 *)
PROG
(PARI) q=vector(10000); h=vector(10000); q[1]=q[2]=1; for(n=3, #q, q[n]=q[n-q[n-1]]+q[n-q[n-2]]); h[1]=h[2]=1; for(n=3, #h, h[n]=h[h[n-1]]+h[n-h[n-1]]); vector(10000, n, (-1)^n*(h[n]-q[n]))
CROSSREFS
KEYWORD
sign,look
AUTHOR
Altug Alkan, Mar 30 2017
STATUS
approved