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A069953
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Composite n such that (n-1)*phi(n) is a perfect square.
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1
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10, 28, 51, 170, 243, 246, 946, 1128, 1281, 1353, 1695, 2431, 4336, 4411, 4625, 4803, 7501, 7936, 8625, 11914, 12545, 13255, 15051, 16385, 24643, 27870, 29404, 31828, 33490, 36751, 39676, 47046, 52801, 53291, 55471, 58807, 66249, 72076, 74061
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| If k>1 k*phi(k) is not a perfect square. Trivially, if p is prime (p-1)*phi(p) is a perfect square.
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PROG
| (PARI) for(n=2, 120000, if(frac(sqrt((n-1+isprime(n))*eulerphi(n)))==0, print1(n, ", ")))
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CROSSREFS
| Sequence in context: A031077 A082286 A088407 * A113746 A177720 A117464
Adjacent sequences: A069950 A069951 A069952 * A069954 A069955 A069956
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 27 2002
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