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A131800 Period 4: repeat 1,2,5,6. +0
2
1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6, 1, 2, 5, 6 (list; graph; listen)
OFFSET

0,2

LINKS

Salvatore Gambino, Terne pitagoriche primitive

FORMULA

a(n) = (7+(-1)^n+4*(-1)^(2*n+1-(-1)^n)/4)/2

O.g.f.: -(1+2x+5x^2+6x^3)/((x-1)(x+1)(x^2+1)) . - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 13 2008

a(n)=(1/6)*{11*(n mod 4)+2*[(n+1) mod 4]-[(n+2) mod 4]+2*[(n+3) mod 4]}, with n>=0 - Paolo P. Lava (ppl(AT)spl.at), Jan 28 2008

a(n)=7/2-(1-I)*I^n-1/2*(-1)^n-(1+I)*(-I)^n, with n>=0 and I=sqrt(-1) - Paolo P. Lava (ppl(AT)spl.at), Jul 17 2008

CROSSREFS

Sequence in context: A111987 A004650 A138279 this_sequence A086038 A134387 A145058

Adjacent sequences: A131797 A131798 A131799 this_sequence A131801 A131802 A131803

KEYWORD

nonn,easy

AUTHOR

Salvatore Gambino (salvatore.gambino(AT)fastwebnet.it), Oct 04 2007

EXTENSIONS

More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 13 2008

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Last modified December 3 01:16 EST 2008. Contains 151161 sequences.


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