A287796 Ten steps forward, nine steps back

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

Table of n, a(n) for n=0..80.

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: A305904 A319345 A213651 * A355675 A073835 A334387

Adjacent sequences: A287793 A287794 A287795 * A287797 A287798 A287799

Keyword

nonn,easy

Author

Wesley Ivan Hurt, May 31 2017

Status

approved