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A069952 Numbers n such that (n+1)*phi(n) is a perfect square. 1
8, 26, 44, 48, 63, 485, 636, 866, 960, 1034, 1351, 1407, 1520, 3970, 4912, 7580, 8749, 12935, 14282, 19601, 20824, 23103, 36480, 43680, 44505, 48599, 49004, 58620, 63000, 72896, 75842, 85696, 90167, 97469, 108240, 122316, 127007, 134135, 134945, 151249 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
If k > 1, then k*phi(k) is not a perfect square. If p is prime, then (p-1)*phi(p) is a perfect square.
LINKS
MATHEMATICA
Select[Range[140000], IntegerQ[Sqrt[EulerPhi[#](#+1)]]&] (* Harvey P. Dale, Jan 21 2013 *)
CROSSREFS
Sequence in context: A328205 A304910 A271989 * A031085 A224481 A031307
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 27 2002
STATUS
approved

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Last modified April 20 15:37 EDT 2024. Contains 371844 sequences. (Running on oeis4.)