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Search: id:A143230
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| 1, 1, 1, 2, 2, 4, 2, 2, 4, 4, 4, 4, 8, 8, 16, 2, 2, 4, 4, 8, 4, 6, 6, 12, 12, 24, 12, 36, 4, 4, 8, 8, 16, 8, 24, 16, 6, 6, 12, 12, 24, 12, 36, 24, 36, 4, 4, 8, 8, 16, 8, 24, 16, 24, 16, 10, 10, 20, 20, 40, 20, 60, 40, 60, 40, 100, 4, 4, 8, 8, 16, 8, 24, 16, 24, 16, 40, 16
(list; table; graph; listen)
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OFFSET
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1,4
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COMMENT
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Left border = A000010.
Row sums = A143231: (1, 2, 8, 12, 40, 24,...).
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FORMULA
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Triangle read by rows, A130207 * A000012 * A130207, where A130207 = A000010 * 0^(n-k), 1<=k<=n. T(n,k) = phi(n) * phi(k), where phi(n) & phi(k) = Euler's totient function.
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EXAMPLE
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First few rows of the triangle =
1;
1, 1;
2, 2, 4;
2, 2, 4, 4;
4, 4, 8, 8, 16;
2, 2, 4, 4, 8, 4;
6, 6, 12, 12, 24, 12, 36;
4, 4, 8, 8, 16, 8, 24, 16;
6, 6, 12, 12, 24, 12, 36, 24, 36;
...
T(7,5) = 24 = phi(7) * phi(5) = 6 * 4
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CROSSREFS
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Cf. A000010, A130207, A143231.
Sequence in context: A077659 A087692 A093621 this_sequence A072301 A127171 A118232
Adjacent sequences: A143227 A143228 A143229 this_sequence A143231 A143232 A143233
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KEYWORD
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nonn,tabl
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AUTHOR
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Gary W. Adamson (qntmpkt(AT)yahoo.com), Jul 31 2008
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