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0, 1, 4, 2, 203, 2597, 3, 5, 16, 14, 12, 10, 8, 6, 97, 15546, 243575589, 404450, 23, 404448, 7, 9, 11, 13, 15, 17, 56, 54, 52, 50, 631, 629, 902, 137, 135, 192, 84974, 84972, 27, 309411696, 131, 22, 20, 18, 85, 111320883, 127, 125
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OFFSET
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0,3
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COMMENTS
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If A274647 is proved to be a permutation, then this is full inverse of it, and the hypothetical -1's are in that case unnecessary (or can be used as markers for yet unknown values).
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LINKS
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Robert Israel, Hugo van der Sanden, Robert Gerbicz, and Benjamin Chaffin Table of a(n) for n = 0..10000. This is based on A274647(n) for n <= 5.4*10^11. The 177 entries of -1 may correspond to values > 5.4*10^11 (first such value is at a(212)).
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FORMULA
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a(n) = index of n in A274647 or -1 if n is not present in that sequence.
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MAPLE
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N = 10^6: # to search A274647(n) for n <= N
A[0]:= 0:B[0]:= 0:
for n from 1 to N do
for k from 1 do
r:= A[n-1]-k*n;
if r > 0 and not assigned(B[r]) then
break
fi;
r:= A[n-1]+k*n;
if not assigned(B[r]) then
break
fi
od;
A[n]:= r;
B[r]:= n;
od:
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PROG
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(Scheme) ;; Use the Scheme-code given in A274647. First one needs to compute A274647 up to some high value of n before trying to list terms of this sequence.
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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