A047315 Numbers that are congruent to {2, 4, 5, 6} mod 7.

2, 4, 5, 6, 9, 11, 12, 13, 16, 18, 19, 20, 23, 25, 26, 27, 30, 32, 33, 34, 37, 39, 40, 41, 44, 46, 47, 48, 51, 53, 54, 55, 58, 60, 61, 62, 65, 67, 68, 69, 72, 74, 75, 76, 79, 81, 82, 83, 86, 88, 89, 90, 93, 95, 96, 97, 100, 102, 103, 104, 107, 109, 110, 111

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A047288, A047385.

Programs

Magma

[n : n in [0..150] | n mod 7 in [2, 4, 5, 6]]; // Wesley Ivan Hurt, Jun 03 2016

Maple

A047315:=n->(14*n-1-I^(2*n)-(3-I)*I^(-n)-(3+I)*I^n)/8: seq(A047315(n), n=1..100); # Wesley Ivan Hurt, Jun 03 2016

Mathematica

Table[(14n-1-I^(2n)-(3-I)*I^(-n)-(3+I)*I^n)/8, {n, 80}] (* Wesley Ivan Hurt, Jun 03 2016 *)
Select[Range[200],MemberQ[{2,4,5,6},Mod[#,7]]&] (* or *) LinearRecurrence[ {1,0,0,1,-1},{2,4,5,6,9},100] (* Harvey P. Dale, Jan 19 2019 *)

Formula

G.f.: x*(2+2*x+x^2+x^3+x^4) / ( (1+x)*(x^2+1)*(x-1)^2 ). - R. J. Mathar, Dec 03 2011

From Wesley Ivan Hurt, Jun 03 2016: (Start)

a(n) = a(n-1) + a(n-4) - a(n-5) for n>5.

a(n) = (14*n-1-i^(2*n)-(3-i)*i^(-n)-(3+i)*i^n)/8 where i=sqrt(-1).

a(2k) = A047288(k), a(2k-1) = A047385(k). (End)