A067879 - OEIS

A067879

Numbers n such that sigma(n)=phi(n*omega(n)+1).

1, 6, 30, 38, 55, 85, 87, 188, 236, 264, 445, 451, 618, 655, 672, 715, 717, 897, 913, 1221, 1265, 1357, 1824, 2095, 2515, 2765, 3009, 3247, 3471, 3605, 3741, 4088, 4117, 4237, 5071, 6747, 7195, 7689, 7701, 8120, 10885, 11577, 12128, 12245, 12549

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OFFSET

1,2

COMMENTS

"Omega(n)" in the definition means the number of distinct prime factors of n, counted without multiplicity. This is implemented in Mathematica as PrimeNu[n] rather than as PrimeOmega[n]. - Harvey P. Dale, Jul 08 2017

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..200

MATHEMATICA

Select[Range[13000], DivisorSigma[1, #]==EulerPhi[#*PrimeNu[#]+1]&] (* Harvey P. Dale, Jul 08 2017 *)

CROSSREFS

Sequence in context: A351844 A345265 A062268 * A334900 A136375 A138706

Adjacent sequences: A067876 A067877 A067878 * A067880 A067881 A067882

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Mar 02 2002

STATUS

approved