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A318707
For any n >= 0 with base-9 representation Sum_{k=0..w} d_k * 9^k, let g(n) = Sum_{k=0..w} s(d_k) * 3^k (where s(0) = 0, s(1+2*j) = i^j and s(2+2*j) = i^j * (1+i) for any j > 0, and i denotes the imaginary unit); a(n) is the square of the modulus of g(n).
2
0, 1, 2, 1, 2, 1, 2, 1, 2, 9, 16, 17, 10, 5, 4, 5, 10, 17, 18, 25, 32, 25, 20, 13, 8, 13, 20, 9, 10, 17, 16, 17, 10, 5, 4, 5, 18, 13, 20, 25, 32, 25, 20, 13, 8, 9, 4, 5, 10, 17, 16, 17, 10, 5, 18, 13, 8, 13, 20, 25, 32, 25, 20, 9, 10, 5, 4, 5, 10, 17, 16, 17
OFFSET
0,3
COMMENTS
See A318705 for the real part of g and additional comments.
LINKS
FORMULA
a(n) = A318705(n)^2 + A318706(n)^2.
a(9 * k) = 9 * a(k) for any k >= 0.
PROG
(PARI) a(n) = my (d=Vecrev(digits(n, 9))); norm(sum(k=1, #d, if (d[k], 3^(k-1)*I^floor((d[k]-1)/2)*(1+I)^((d[k]-1)%2), 0)))
CROSSREFS
Sequence in context: A336336 A168580 A356206 * A363228 A235726 A060938
KEYWORD
nonn,base,look
AUTHOR
Rémy Sigrist, Sep 01 2018
STATUS
approved