A290781 a(n) = 20*n + 15.

15, 35, 55, 75, 95, 115, 135, 155, 175, 195, 215, 235, 255, 275, 295, 315, 335, 355, 375, 395, 415, 435, 455, 475, 495, 515, 535, 555, 575, 595, 615, 635, 655, 675, 695, 715, 735, 755, 775, 795, 815, 835, 855, 875, 895, 915, 935, 955, 975, 995, 1015, 1035

Offset: 0

Author

Arkadiusz Wesolowski, Aug 10 2017

Keywords

• nonn
• easy

Comments

Bisection of A017329.

None of the numbers in this sequence is a Fermat pseudoprime to base 2.

Links

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

Crossrefs

Cf. A001567, A004767, A008587, A016885, A017329.

Programs

Magma

[n: n in [15..1035 by 20]];

Mathematica

Range[15, 1035, 20]

Formula

G.f.: 5*(3 + x)/(1 - x)^2.

a(n) = A004767(A016885(n)) = A004767(A004767(n) + n). - Torlach Rush, Oct 10 2019

E.g.f.: 5*exp(x)*(3 + 4*x). - Stefano Spezia, Oct 12 2019

From Elmo R. Oliveira, Apr 12 2025: (Start)

a(n) = 5*A004767(n) = A017329(2*n+1) = A008587(4*n+3).

a(n) = 2*a(n-1) - a(n-2). (End)