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URL: https://oeis.org/A229822

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A229822
Even bisection gives sequence a itself, n->a(2*(7*n+k)-1) gives k-th differences of a for k=1..7 with a(n)=n for n<2.
9
0, 1, 1, -1, 1, -1, -1, 7, 1, -21, -1, 49, -1, -91, 7, 0, 1, -2, -21, 6, -1, -14, 49, 28, -1, -42, -91, 28, 7, -2, 0, 4, 1, -8, -2, 14, -21, -14, 6, -14, -1, 90, -14, 2, 49, -4, 28, 6, -1, 0, -42, -28, -91, 76, 28, -84, 7, -2, -2, 2, 0, 6, 4, -28, 1, 48, -8
OFFSET
0,8
LINKS
FORMULA
a(2*n) = a(n),
a(2*(7*n+k)-1) = Sum_{j=0..k} (-1)^j * C(k,j) * a(n+k-j) for k=1..7.
MAPLE
a:= proc(n) option remember; local m, q, r;
m:= (irem(n, 14, 'q')+1)/2;
`if`(n<2, n, `if`(irem(n, 2, 'r')=0, a(r),
add(a(q+m-j)*(-1)^j*binomial(m, j), j=0..m)))
end:
seq(a(n), n=0..100);
MATHEMATICA
a[n_] := a[n] = Module[{m, q, r, q2, r2}, {q, r} = QuotientRemainder[n, 14]; m = (r+1)/2; If[n<2, n, {q2, r2} = QuotientRemainder[n, 2]; If[r2 == 0, a[q2], Sum[a[q+m-j]*(-1)^j*Binomial[m, j], {j, 0, m}]]]]; Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Mar 08 2017, translated from Maple *)
KEYWORD
sign,eigen
AUTHOR
Alois P. Heinz, Sep 30 2013
STATUS
approved