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A022157
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n^2 - phi(n)*tau(n)^2.
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1
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0, 0, 1, -2, 9, 4, 25, 0, 27, 36, 81, 0, 121, 100, 97, 56, 225, 108, 289, 112, 249, 324, 441, 64, 445, 484, 441, 352, 729, 388, 841, 448, 769, 900, 841, 324, 1225, 1156, 1137, 576, 1521, 996, 1681, 1216, 1161, 1764, 2025, 704, 2023, 1780
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| a(n)>=0 for n != 4. a(n)=0 iff n=1,2,8,12.
An example of a sequence constructed from an arithmetic inequality.
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REFERENCES
| S. Porubsky, Problem E2351, Amer. Math. Monthly, 80 (1973), 436.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..2000
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MAPLE
| with(numtheory); [ seq(n^2-phi(n)*tau(n)^2, n=1..100) ];
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CROSSREFS
| Sequence in context: A021343 A200703 A080803 * A065599 A171228 A171560
Adjacent sequences: A022154 A022155 A022156 * A022158 A022159 A022160
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KEYWORD
| sign,easy,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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