A144429 Starts 1 2 3 then successive terms have differences 1 2 3.

1, 2, 3, 4, 6, 9, 10, 12, 15, 16, 18, 21, 22, 24, 27, 28, 30, 33, 34, 36, 39, 40, 42, 45, 46, 48, 51, 52, 54, 57, 58, 60, 63, 64, 66, 69, 70, 72, 75, 76, 78, 81, 82, 84, 87, 88, 90, 93, 94, 96, 99, 100, 102, 105, 106, 108, 111, 112, 114, 117, 118, 120, 123, 124, 126, 129

Offset

1,2

Comments

Essentially the same sequence as A047231. - Stefan Steinerberger, Oct 17 2008

Links

Table of n, a(n) for n=1..66.

Index entries for linear recurrences with constant coefficients, signature (1, 0, 1, -1).

Formula

G.f.: x(1+x)(1+x^2-x^3+2x^4)/((1+x+x^2)(1-x)^2). a(n)=a(n-3)+6, n>5. a(n) = 2n -11/3 +A099837(n+3)/3, n>2. [From R. J. Mathar, Oct 15 2008]

Mathematica

Join[{1, 2}, LinearRecurrence[{1, 0, 1, -1}, {3, 4, 6, 9}, 100]] (* or *) nxt[ {a_, b_, c_}]:= {c+1, c+3, c+6}; Flatten[NestList[nxt, {1, 2, 3}, 30]] (* Harvey P. Dale, Nov 23 2012 *)

Crossrefs

Cf. A144430, A047231.

Sequence in context: A285082 A249602 A119761 * A260194 A014851 A177919

Adjacent sequences: A144426 A144427 A144428 * A144430 A144431 A144432

Keyword

nonn,easy

Author

Milton L. Brown (miltbrown(AT)earthlink.net), Oct 13 2008

Extensions

Extended by R. J. Mathar, Oct 15 2008

Status

approved