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Search: id:A120879
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| A120879 |
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G.f. satisfies: A(x) = A(x^3)*(1 + 3*x + 2*x^2); thus a(n) = 3^A062756(n) * 2^A081603(n), where A062756(n) is the number of 1's and A081603(n) is the number of 2's, in the ternary expansion of n. |
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+0
1
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| 1, 3, 2, 3, 9, 6, 2, 6, 4, 3, 9, 6, 9, 27, 18, 6, 18, 12, 2, 6, 4, 6, 18, 12, 4, 12, 8, 3, 9, 6, 9, 27, 18, 6, 18, 12, 9, 27, 18, 27, 81, 54, 18, 54, 36, 6, 18, 12, 18, 54, 36, 12, 36, 24, 2, 6, 4, 6, 18, 12, 4, 12, 8, 6, 18, 12, 18, 54, 36, 12, 36, 24, 4, 12, 8, 12, 36, 24, 8, 24, 16, 3, 9
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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If g.f. of {a(n)} satisfies: A(x) = A(x^d)*(1+Sum_{k=1..d-1} c(k)*x^k), then a(n) = prod_{k=1..d-1} c(k)^digits(n,k,d), where digits(n,k,d) is the number of k's in the d-ary expansion of n and d is any integer > 1. This sequence is a simple example for d=3 with c(1)=3 and c(2)=2.
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FORMULA
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G.f.: A(x) = prod_{n>=0} (1 + x^(3^n))*(1 + 2*x^(3^n)). Recurrence: a(n) = a(floor(n/3)) * 3^((n Mod3) Mod2) * 2^floor((n Mod3)/2) with a(0)=1.
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PROGRAM
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(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(i=1, floor(log(n+1)/log(3))+1, A=subst(A, x, x^3+x*O(x^n))*(1+3*x+2*x^2)); polcoeff(A, n, x)} (PARI) /* Recurrence: */ {a(n)=if(n==0, 1, a(n\3)*3^((n%3)%2)*2^((n%3)\2))}
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CROSSREFS
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Cf. A120880, A062756, A081603.
Sequence in context: A049921 A022460 A010605 this_sequence A078017 A057053 A081850
Adjacent sequences: A120876 A120877 A120878 this_sequence A120880 A120881 A120882
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Jul 11 2006
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