A173777 Infinite sequence gradually builds a triangle plus another more widely spaced triangle on top of it, or overlapping, if you will.

2, 2, 2, 2, 3, 3, 4, 5, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 18, 19, 21, 23, 24, 26, 28, 30, 32, 34, 36, 38, 41, 43, 45, 48, 50, 53, 56, 58, 61, 64, 67, 70, 73, 76, 79, 83, 86, 89, 93, 96, 100, 104, 107, 111, 115, 119, 123, 127, 131, 135, 140, 144, 148, 153, 157, 162, 167

Offset

1,1

Comments

This sequence almost builds a square (two triangles with the sparse triangle rotated), but not quite.

Links

Eric Werner, Table of n, a(n) for n = 1..311

Formula

Conjectures from Colin Barker, Dec 01 2019: (Start)

G.f.: x*(2 - 2*x^3 + x^4 - 2*x^5 + x^6 + 2*x^8 - x^9) / ((1 - x)^3*(1 + x + x^2)*(1 + x + x^2 + x^3 + x^4)).

a(n) = a(n-1) + a(n-3) - a(n-4) + a(n-5) - a(n-6) - a(n-8) + a(n-9) for n>10.

(End)

Crossrefs

Sequence in context: A200245 A116492 A103263 * A140436 A236916 A029083

Adjacent sequences: A173774 A173775 A173776 * A173778 A173779 A173780

Keyword

nonn,obsc,uned

Author

Eric Werner (eric.werner(AT)gmx.net), Feb 24 2010

Status

approved