A131042 Natural numbers A000027 with 6n+3 and 6n+4 terms swapped.

1, 2, 4, 3, 5, 6, 7, 8, 10, 9, 11, 12, 13, 14, 16, 15, 17, 18, 19, 20, 22, 21, 23, 24, 25, 26, 28, 27, 29, 30, 31, 32, 34, 33, 35, 36, 37, 38, 40, 39, 41, 42, 43, 44, 46, 45, 47, 48, 49, 50, 52, 51, 53, 54, 55, 56, 58, 57, 59, 60, 61, 62, 64, 63, 65, 66, 67, 68, 70, 69, 71, 72

Offset

1,2

Links

Colin Barker, Table of n, a(n) for n = 1..1000

Index entries for sequences that are permutations of the natural numbers

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

Formula

a(n) = (24*floor(n/6)+3*n^2-3*n+8+9*floor(n/3)*(3*floor(n/3)-2*n+1)-(3*n^2-7*n+8+3*floor(n/3)*(9*floor(n/3)-6*n+7))*(-1)^floor(n/3))/4. - Luce ETIENNE, Apr 08 2017

From Colin Barker, Apr 08 2017: (Start)

G.f.: x*(1 + x + 2*x^2 - x^3 + 2*x^4 + x^5) / ((1 - x)^2*(1 + x)*(1 - x + x^2)*(1 + x + x^2)).

a(n) = a(n-1) + a(n-6) - a(n-7) for n>7.

(End)

Prog

(PARI) Vec(x*(1 + x + 2*x^2 - x^3 + 2*x^4 + x^5) / ((1 - x)^2*(1 + x)*(1 - x + x^2)*(1 + x + x^2)) + O(x^100)) \\ Colin Barker, Apr 08 2017

Crossrefs

Sequence in context: A228083 A222234 A362075 * A274631 A368181 A275335

Adjacent sequences: A131039 A131040 A131041 * A131043 A131044 A131045

Keyword

nonn,easy

Author

Paul Curtz, Sep 23 2007

Status

approved