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A067811 Numbers n such that phi(n)^2 + sigma(n)^2 is an integer square. 1
7, 32, 33, 41, 68, 145, 209, 237, 239, 266, 328, 372, 384, 385, 442, 522, 622, 905, 945, 1157, 1243, 1288, 1357, 1581, 1615, 1643, 1798, 1853, 1885, 1978, 1995, 2093, 2418, 2541, 2698, 2765, 2769, 2981, 3013, 3161, 3315, 3451, 3519, 3577, 4041, 4309, 4318 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

phi(32)^2 + sigma(32)^2 = 16^2 + 63^2 = 4225 = 65^2, so 32 is a term of the sequence.

MATHEMATICA

Select[Range[10^4], IntegerQ[Sqrt[EulerPhi[ # ]^2 + DivisorSigma[1, # ]^2]] &]

PROG

(PARI) isok(n) = issquare(eulerphi(n)^2+sigma(n)^2); \\ Michel Marcus, Aug 13 2019

CROSSREFS

Cf. A000010, A000203.

Sequence in context: A193637 A214490 A164819 * A044084 A044465 A029484

Adjacent sequences:  A067808 A067809 A067810 * A067812 A067813 A067814

KEYWORD

easy,nonn

AUTHOR

Joseph L. Pe, Feb 07 2002

STATUS

approved

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Last modified February 24 22:04 EST 2020. Contains 332216 sequences. (Running on oeis4.)