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A055971 Numbers n such that n | Sigma(n) - d(n) - Phi(n) and n is not a prime or twice a prime, where d(n) is the number of divisors of n. 1
1, 198, 294, 20280, 195320, 1782240, 3038720, 12190720 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..8.

MATHEMATICA

Do[ If[ And[ !PrimeQ[ n ], !PrimeQ[ n/2 ] ], If[ Mod[ DivisorSigma[ 1, n ]-DivisorSigma[ 0, n ]- EulerPhi[ n ], n ]==0, Print[ n ] ] ], {n, 1, 10^8} ]

CROSSREFS

Sequence in context: A025366 A248534 A238230 * A075293 A083264 A202526

Adjacent sequences:  A055968 A055969 A055970 * A055972 A055973 A055974

KEYWORD

easy,nonn

AUTHOR

Robert G. Wilson v, Jul 19 2000

STATUS

approved

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Last modified March 25 10:31 EDT 2019. Contains 321470 sequences. (Running on oeis4.)