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A287796
Ten steps forward, nine steps back
1
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 5, 6, 7, 8
OFFSET
0,3
LINKS
Index entries for linear recurrences with constant coefficients, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1).
FORMULA
a(n) = Sum_{i=1..n} (-1)^floor((2*i-2)/19).
a(n) = a(n-1) + a(n-19) - a(n-20) for n > 19.
MAPLE
A287796:=n->add((-1)^floor((2*i-2)/19), i=1..n): seq(A287796(n), n=0..200);
MATHEMATICA
Table[Sum[(-1)^Floor[(2 i - 2)/19], {i, n}], {n, 0, 100}]
CROSSREFS
Cf. A008611 (one step back, two steps forward).
Cf. A058207 (three steps forward, two steps back).
Cf. A260644 (four steps forward, three steps back).
Cf. A271800 (five steps forward, four steps back).
Cf. A271859 (six steps forward, five steps back).
Cf. A287655 (seven steps forward, six steps back).
Cf. A287793 (eight steps forward, seven steps back).
Cf. A287794 (nine steps forward, eight steps back).
Sequence in context: A319345 A376769 A213651 * A355675 A073835 A334387
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, May 31 2017
STATUS
approved