A037740 Base-7 digits are, in order, the first n terms of the periodic sequence with initial period 2,1,3,0.

2, 15, 108, 756, 5294, 37059, 259416, 1815912, 12711386, 88979703, 622857924, 4360005468, 30520038278, 213640267947, 1495481875632, 10468373129424, 73278611905970, 512950283341791, 3590651983392540

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..100

Index entries for linear recurrences with constant coefficients, signature (7,0,0,1,-7).

Formula

a(n) = 7*a(n-1) + a(n-4) - 7*a(n-5). - Charles R Greathouse IV, Jan 16 2011

G.f.: x*(3*x^2 + x + 2)/(7*x^5 - x^4 - 7*x + 1). - Harvey P. Dale, Sep 18 2011

a(n) = (63*7^n + (7-(-1)^n)*(25+2*i^(n*(n+1))) - 225)/200, where i=sqrt(-1). - Bruno Berselli, Sep 19 2011

Mathematica

LinearRecurrence[{7, 0, 0, 1, -7}, {2, 15, 108, 756, 5294}, 30] (* Harvey P. Dale, Sep 18 2011 *)

Prog

(Magma) I:=[2, 15, 108, 756, 5294]; [n le 5 select I[n] else 7*Self(n-1)+Self(n-4)-7*Self(n-5): n in [1..20]]; // Vincenzo Librandi, Sep 19 2011

Crossrefs

Sequence in context: A037572 A218686 A279087 * A037635 A154635 A062808

Adjacent sequences: A037737 A037738 A037739 * A037741 A037742 A037743

Keyword

nonn,base,easy

Author

Clark Kimberling

Status

approved