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A131866
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Distance of n-th semiprime to nearest square.
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0
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0, 2, 0, 1, 2, 1, 4, 3, 0, 1, 3, 2, 1, 2, 3, 3, 0, 2, 6, 7, 6, 2, 1, 5, 7, 4, 1, 4, 5, 6, 9, 7, 6, 5, 6, 10, 6, 3, 2, 0, 1, 2, 8, 11, 10, 3, 2, 1, 1, 2, 11, 11, 10, 8, 3, 0, 8, 9, 13, 11, 9, 2, 5, 6, 7, 9, 10, 13, 12, 11, 10, 8, 7, 6, 4, 1, 10, 12, 9, 7, 3, 2, 3, 6, 9, 11, 15, 11, 2, 0, 2, 6, 9, 10, 12
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| This to semiprimes A001358 as A047972 is to primes A000040.
For each semiprime, find the closest square (preceding or succeeding); subtract, take absolute value.
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FORMULA
| a(n)=A053188(A001358(n)) (corrected by R. J. Mathar, Nov 19 2007).
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EXAMPLE
| a(1) = 0 because the first semiprime is 4, which is a square.
a(2) = 2 because the 2nd semiprime is 6 and |6-4| = 2 where 4 is the nearest square to 6.
a(3) = 0 because the 3rd semiprime is 9, which is a square.
a(4) = 1 because the 4th semiprime is 10 and |10-9| = 1 where 9 is the nearest square to 10.
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CROSSREFS
| Cf. A001358, A047972, A053188.
Sequence in context: A020513 A029276 A109248 * A036862 A094238 A127793
Adjacent sequences: A131863 A131864 A131865 * A131867 A131868 A131869
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KEYWORD
| easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Oct 04 2007
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 24 2007
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