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Search: id:A131866
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| A131866 |
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Distance of n-th semiprime to nearest square. |
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+0
1
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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; listen)
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OFFSET
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1,2
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COMMENT
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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
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a(n)=A053188(A001358(n)) (corrected by R. J. Mathar, Nov 19 2007).
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EXAMPLE
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a(1) = 0 because the 1st 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
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Cf. A001358, A047972, A053188.
Sequence in context: A020513 A029276 A109248 this_sequence A036862 A094238 A127793
Adjacent sequences: A131863 A131864 A131865 this_sequence A131867 A131868 A131869
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Oct 04 2007
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 24 2007
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