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Search: id:A160467
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| A160467 |
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The fifth factor of the row sums of the Eta triangle A160464 |
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2
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| 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 8, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 16, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 8, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 32, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 8, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 16
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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Contribution from Peter Luschny (peter(AT)luschny.de), May 31 2009: (Start)
Let odd(n) by the characteristic function of the odd numbers (A000035) and sigma(n) the number of 1's in binary expansion of n (A000120) then
a(n) = 2^(sigma(n-1)-sigma(n)+odd(n)).
Let B_{n} be the Bernoulli number. Then this sequence is also
a(n) = denominator(4*(4^n-1)*B_{2*n}/n). (End)
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MAPLE
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nmax:=96; p:= floor(ln(nmax)/ln(2)): for n from 1 to nmax do c(n):=1 end do: for q from 1 to p do for n from 1 to nmax do if n mod 2^q = 0 then c(n):=2^(q-1) end if: end do: end do: a:=n-> c(n): seq(a(n), n=1..nmax);
Contribution from Peter Luschny (peter(AT)luschny.de), May 31 2009: (Start)
a := proc(n) local sigma; sigma := proc(n) local i; add(i, i=convert(n, base, 2)) end; 2^(sigma(n-1)-sigma(n)+`if`(type(n, odd), 1, 0)) end;
a2 := proc(n) denom(4*(4^n-1)*bernoulli(2*n)/n) end; (End)
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CROSSREFS
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Fifth factor of the row sums A160466 of the Eta triangle A160464.
Sequence in context: A054772 A085384 A067856 this_sequence A122374 A010121 A157114
Adjacent sequences: A160464 A160465 A160466 this_sequence A160468 A160469 A160470
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KEYWORD
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base,easy,nonn
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AUTHOR
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Johannes W. Meijer (meijgia(AT)hotmail.com), May 24 2009
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