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A193564
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In A014675, replace the n-th occurrence of 1 with n-1 and also replace the n-th occurrence of 2 with n-1.
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2
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0, 0, 1, 2, 1, 3, 2, 4, 5, 3, 6, 7, 4, 8, 5, 9, 10, 6, 11, 7, 12, 13, 8, 14, 15, 9, 16, 10, 17, 18, 11, 19, 20, 12, 21, 13, 22, 23, 14, 24, 15, 25, 26, 16, 27, 28, 17, 29, 18, 30, 31, 19, 32, 20, 33, 34, 21, 35, 36, 22, 37, 23, 38, 39, 24, 40, 41, 25, 42
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OFFSET
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1,4
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COMMENTS
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An infinite sequence of Langford pairs.
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REFERENCES
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D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7, p. 36.
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LINKS
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MAPLE
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A000201 := proc(n) option remember; floor(n*(1+sqrt(5))/2) ; end proc:
A193564aux := proc(n, piv) local oc, j ; oc := 0 ; for j from 0 to n do if A014675(j) = piv then oc := oc+1 ; end if; end do: oc ; end proc:
A193564 := proc(n) local piv, oc ; piv := A014675(n-1) ; oc := A193564aux(n-1, piv) ; oc-1 ; end proc:
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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