A355492 a(n) = 7*3^n - 2.

5, 19, 61, 187, 565, 1699, 5101, 15307, 45925, 137779, 413341, 1240027, 3720085, 11160259, 33480781, 100442347, 301327045, 903981139, 2711943421, 8135830267, 24407490805, 73222472419, 219667417261, 659002251787, 1977006755365, 5931020266099, 17793060798301, 53379182394907

Offset

0,1

Comments

Right ending points of the gaps in A171884. The left ending points are given in A198643.

Links

Jianing Song, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (4,-3).

Formula

G.f.: (5-x)/((1-x)*(1-3*x)).

E.g.f.: 7*exp(3*x) - 2*exp(x).

Example

The numbers not appearing in A171884 are those in the range [5*3^k-1, 7*3^k-2] for some k; that is, [4, 5] U [14, 19] U [44, 61] U ...

Mathematica

7*3^Range[0, 50] - 2 (* Paolo Xausa, Jun 10 2024 *)

Prog

(PARI) a(n)=7*3^n-2

Crossrefs

Cf. A171884, A198643.

Sequence in context: A036644 A000342 A189427 * A212339 A072111 A173627

Adjacent sequences: A355489 A355490 A355491 * A355493 A355494 A355495

Keyword

nonn,easy

Author

Jianing Song, Oct 07 2022

Status

approved