A094103 a(n) = sum along n-th diagonal of A094102 (sloping downward to left).

1, 1, 2, 3, 4, 5, 8, 9, 13, 16, 22, 26, 37, 43, 60, 71, 98, 115, 160, 187, 259, 304, 420, 492, 681, 797, 1102, 1291, 1784, 2089, 2888, 3381, 4673, 5472, 7562, 8854, 12237, 14327, 19800, 23183, 32038, 37511, 51840, 60695, 83879, 98208, 135720, 158904, 219601

Offset: 1

Author

Alysia Veenhof (ladyluck1899(AT)hotmail.com), May 05 2004

Keywords

• nonn
• easy
• changed

Examples

			a(8) = 2+3+2+1+1 = 9.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (0,1,1,1,-1,0,-1).

Crossrefs

Cf. A094102.

Programs

Mathematica

CoefficientList[Series[(1+x+x^2+x^3)/((1-x^3)(1-x^2-x^4)),{x,0,60}],x] (* or *) LinearRecurrence[{0,1,1,1,-1,0,-1},{1,1,2,3,4,5,8},61] (* Harvey P. Dale, Oct 09 2011 *)

Formula

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

a(1)=1, a(2)=1, a(3)=2, a(4)=3, a(5)=4, a(6)=5, a(7)=8, a(n) = a(n-2)+a(n-3)+a(n-4)-a(n-5)-a(n-7). - Harvey P. Dale, Oct 09 2011

Extensions

More terms from Pab Ter (pabrlos(AT)yahoo.com), May 24 2004