A087775 a[1] = 1, a[2] = 2, a[3] = 2; a[n] = 3*a[abs[a[n-2]]] - 3*a[n-abs[a[n-2]]] + a[n-3].

1, 2, 2, 1, 2, -1, 1, 2, -4, 1, 2, -7, 1, 2, -10, 1, 2, -13, 1, 2, -16, 1, 2, -19, 1, 2, -22, 1, 2, -25, 1, 2, -28, 1, 2, -31, 1, 2, -34, 1, 2, -37, 1, 2, -40, 1, 2, -43, 1, 2, -46, 1, 2, -49, 1, 2, -52, 1, 2, -55, 1, 2, -58, 1, 2, -61, 1, 2, -64, 1, 2, -67, 1, 2, -70, 1, 2, -73, 1, 2, -76, 1, 2, -79, 1, 2, -82, 1, 2, -85, 1, 2, -88, 1, 2, -91, 1, 2

Offset

1,2

Comments

A recursive sequence based on A087774 and the Mallows A005229 sequence. A tick-tock sequence where the form is: 1,2,a(n-3)-3

Links

Table of n, a(n) for n=1..98.

Mathematica

hg[n_Integer?Positive] := hg[n] =3*hg[Abs[hg[n-2]]] -3*hg[n-Abs[hg[n-2]]]+hg[n-3] hg[1] =1 hg[2] =2 hg[3]=2 digits=200 a=Table[hg[n], {n, 1, digits}]

Crossrefs

Cf. A005229.

Sequence in context: A322156 A332278 A182596 * A366091 A089955 A352942

Adjacent sequences: A087772 A087773 A087774 * A087776 A087777 A087778

Keyword

sign

Author

Roger L. Bagula, Oct 04 2003

Status

approved