A133043 Number of segments needed to draw the spiral of equilateral triangles with side lengths which follow the Padovan sequence.

3, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65

Offset: 1

Author

Omar E. Pol, Nov 04 2007, Nov 05 2007

Keywords

• easy
• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (2,-1).

Crossrefs

Cf. Padovan sequence: A000931.

Programs

Mathematica

LinearRecurrence[{2,-1},{3,5,6,8,9},70] (* Harvey P. Dale, Dec 21 2018 *)

PARI

a(n)=if(n>3,n+4,[3,5,6][n]) \\ Charles R Greathouse IV, Oct 27 2011

Formula

a(1)=3: a(2)=5: a(3)=6; for n>3, a(n)=n+4.