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A122483 Numbers such that (-1)Sigma(m)*Sigma(m)= k*UnitaryPhi(m)*m for some integer k. 1
6, 140, 312, 1560, 14384, 18018, 40992, 2337400, 7012200, 11027016, 231402600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If both 2^n-3 and 2^n-1 are prime them numbers of the form 2^(n-1)*(M_n-2)*M_n appear on the sequence, where M_n means Mersenne prime.

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

2^8*7*19*37*73*509, 2^8*5*7*19*37*509, 2^8*5^2*7*19*29*31*37*509, 2^9*3*11*31*1021, 2^9*3*7*11^2*19*31*131*1021, 2^11*3^6*5*7*13*23*137*467*1093*4093, 2^13*3*11*43*127*16381, 2^13*3*7*11^2*19*43*127*131*16381 But between 3*10^7 and them, many terms may lack.

CROSSREFS

Cf. A123124.

Sequence in context: A053467 A090944 A007340 * A123729 A193835 A123728

Adjacent sequences:  A122480 A122481 A122482 * A122484 A122485 A122486

KEYWORD

nonn,more

AUTHOR

Yasutoshi Kohmoto, Sep 30 2006

EXTENSIONS

More terms from R. J. Mathar, Oct 01 2006

STATUS

approved

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Last modified December 8 09:03 EST 2016. Contains 278906 sequences.