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1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4, 1, 7, 4
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refs;
listen;
history;
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OFFSET
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0,2
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COMMENTS
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Also the digital root of 7^n. If we convert this to a repeating decimal 0.174174.., we get the rational number 58/333. - Cino Hilliard (hillcino368(AT)gmail.com), Dec 31 2004
A141722 (1, 25, 121, 505, 2041, 8185) mod 9 . Note A141722=10*A000975(2n)+A000975(2n+1). [From Paul Curtz, Sep 15 2008]
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LINKS
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Table of n, a(n) for n=0..104.
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FORMULA
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a(n)=(1/3)*{7*(n mod 3)+7*[(n+1) mod 3]-2*[(n+2) mod 3]}, with n>=0 [From Paolo P. Lava, Oct 21 2008]
G.f.: (1+7x+4x^2)/((1-x)(1+x+x^2)). a(n+1)-a(n)=3*A099837(n+3). a(n)=4-3*A049347(n). [From R. J. Mathar, Feb 23 2009]
a(n)=4+4/3*(-1/2-(1/2*I)*sqrt(3))^(-2)*(-1/2-(1/2*I)*sqrt(3))^n+4/3*(-1/2+(1/2*I) *sqrt(3))^(-2)*(-1/2+(1/2*I)*sqrt(3))^n+1/3*(-1/2-(1/2*I)*sqrt(3))^n+1/3*(-1/2 +(1/2*I)*sqrt(3))^n+7/3*(-1/2-(1/2*I)*sqrt(3))^(-1)*(-1/2-(1/2*I)*sqrt(3))^n+7/3 *(-1/2+(1/2*I)*sqrt(3))^(-1)*(-1/2+(1/2*I)*sqrt(3))^n, with n>=0 and I=sqrt(-1) [From Paolo P. Lava, Feb 25 2010]
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MATHEMATICA
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Table[PowerMod[7, n, 9], {n, 0, 200}] (* From Vladimir Joseph Stephan Orlovsky, Jun 10 2011 *)
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PROG
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(Sage) [power_mod(7, n, 9)for n in xrange(0, 105)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Nov 03 2009]
(MAGMA)[7^n mod 9: n in [0..80]]; [From Vincenzo Librandi, Feb 07 2011]
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CROSSREFS
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Sequence in context: A010138 A199157 A010508 * A144468 A059630 A011407
Adjacent sequences: A070400 A070401 A070402 * A070404 A070405 A070406
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, May 12 2002
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STATUS
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approved
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