A079355 a(1) = 1; a(n) = a(n-1)-3 if n is already in the sequence, a(n) = a(n-1)+4 otherwise.

1, 5, 9, 13, 10, 14, 18, 22, 19, 16, 20, 24, 21, 18, 22, 19, 23, 20, 17, 14, 11, 8, 5, 2, 6, 10, 14, 18, 22, 26, 30, 34, 38, 35, 32, 36, 40, 37, 41, 38, 35, 39, 43, 47, 51, 55, 52, 56, 60, 64, 61, 58, 62, 66, 63, 60, 64, 61, 65, 62, 59, 56, 53, 50, 47, 44, 48, 52, 56, 60, 64, 68

Offset

1,2

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Index entries for linear recurrences with constant coefficients, order 43.

Formula

a(n) = n+b(n)-22 where b(n) is the 42-periodic sequence (22, 25, 28, 31, 27, 30, 33, 36, 32, 28, 31, 34, 30, 26, 29, 25, 28, 24, 20, 16, 12, 8, 4, 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 23, 19, 22, 25, 21, 24, 20, 16, 19)

a(n) = +a(n-1) +a(n-42) -a(n-43). - R. J. Mathar, Mar 16 2026

Maple

A079355 := proc(n)
    option remember ;
    if n =1 then
        1;
    else
        fnd := false ;
        for j from 1 to n-1 do
            if procname(j) = n then
                fnd := true ;
                break ;
            end if;
        end do;
        if fnd then
            procname(n-1)-3 ;
        else
            procname(n-1)+4 ;
        end if;
    end if;
end proc:
seq(A079355(n), n=1..100) ; # R. J. Mathar, Mar 16 2026

Mathematica

A079355list[nmax_] := Module[{s, a}, s[_] := False; s[1] = True; FoldList[(s[a = # + If[s[#2], -3, 4]] = True; a) &, Range[nmax]]];
A079355list[100] (* or *)
A079355[n_] := n + {19, 22, 25, 28, 31, 27, 30, 33, 36, 32, 28, 31, 34, 30, 26, 29, 25, 28, 24, 20, 16, 12, 8, 4, 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 23, 19, 22, 25, 21, 24, 20, 16}[[Mod[n, 42] + 1]] - 22;
Array[A079355, 100] (* Paolo Xausa, Mar 25 2026 *)

Crossrefs

Cf. A079357.

Sequence in context: A277617 A103703 A143706 * A080781 A079357 A080455

Adjacent sequences: A079352 A079353 A079354 * A079356 A079357 A079358

Keyword

nonn,hear,easy

Author

Benoit Cloitre, Feb 14 2003

Status

approved