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A037740
Base-7 digits are, in order, the first n terms of the periodic sequence with initial period 2,1,3,0.
2
2, 15, 108, 756, 5294, 37059, 259416, 1815912, 12711386, 88979703, 622857924, 4360005468, 30520038278, 213640267947, 1495481875632, 10468373129424, 73278611905970, 512950283341791, 3590651983392540
OFFSET
1,1
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
KEYWORD
nonn,base,easy
STATUS
approved