A228967 Table read by rows; T(n,k) = 2n for k = 1, T(n,k) = 9n for k = 2.

2, 9, 4, 18, 6, 27, 8, 36, 10, 45, 12, 54, 14, 63, 16, 72, 18, 81, 20, 90, 22, 99, 24, 108, 26, 117, 28, 126, 30, 135, 32, 144, 34, 153, 36, 162, 38, 171, 40, 180, 42, 189, 44, 198, 46, 207, 48, 216, 50, 225, 52, 234, 54, 243, 56, 252, 58, 261, 60, 270, 62, 279, 64, 288

Offset

1,1

Comments

Each pair of [T(n,1),T(n,2)] creates the same sequences of circle curvature (rounded down), after offset of the first 4 terms. See the pattern construction rule and formulas in links. Let the legs length a = b = T(n,k). See also illustration in links; the pair of [T(1,1),T(1,2)] creates the same sequences but different from the pair of [T(2,1),T(2,2)]. Are they have repeated sequences between pairs?

Positive terms of A005843 and positive terms of A008591 interleaved. - Omar E. Pol, Sep 14 2013

Links

Table of n, a(n) for n=1..64.

Kival Ngaokrajang, Illustration for [T(1,1),T(1,2)] and [T(2,1),T(2,2)]

Eric Weisstein's World of Mathematics, Right Triangle

Index entries for linear recurrences with constant coefficients, signature (0,2,0,-1).

Formula

a(n) = 2a(n-2) - a(n-4). - Charles R Greathouse IV, Sep 10 2013

Example

Table begins:
n/k  1  2
1    2  9
2    4  18
3    6  27
4    8  36
...

Mathematica

LinearRecurrence[{0, 2, 0, -1}, {2, 9, 4, 18}, 80] (* Harvey P. Dale, Sep 21 2019 *)

Prog

(PARI) vector(80, n, (n+1)\2*if(n%2, 2, 9)) \\ Charles R Greathouse IV, Sep 10 2013

Crossrefs

Sequence in context: A080803 A370500 A339316 * A342661 A213821 A022157

Adjacent sequences: A228964 A228965 A228966 * A228968 A228969 A228970

Keyword

nonn,easy,tabf

Author

Kival Ngaokrajang, Sep 10 2013

Extensions

Corrected by Charles R Greathouse IV, Sep 10 2013

Status

approved