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 A137817 Cubeful "year numbers" (such that phi(n) = 2 phi(sigma(n)): A137815). 3
 295569, 295947, 1586763, 1811079, 1964375, 2069469, 4473387, 5854375, 6820555, 7285923, 10936053, 12233457, 13260625, 18029709, 18052767, 21153663, 21576537, 21604131, 22182093, 22877451, 23744043, 25536875, 28340307, 34102775 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS See A137815 for general comments and references about "year numbers". This is the subsequence of cubeful elements of A137815, i.e. its intersection with A046099. As such, it is of course also a subsequence of A137816. There are only 56 such numbers below 10^8. LINKS M. F. Hasler and Donovan Johnson, Table of n, a(n) for n = 1..1000 (first 56 terms from M. F. Hasler) PROG (PARI) for( i=1, #A137816, vecmax( factor( A137816[i] )[, 2])>2 && print1(A137816[i]", ")) (PARI) for( i=1, #A046099, eulerphi(A046099[i])==2*eulerphi(sigma(A046099[i])) && print1( A046099[i] ", ")) (PARI) for( n=1, 10^9, issquarefree(n) && next; vecmax(factor(n)[, 2])>2 || next; eulerphi(n)==2*eulerphi(sigma(n)) && print1(n", ")) CROSSREFS Cf. A137815-A137819, A006872. A046099. A067704. Sequence in context: A258527 A254919 A109031 * A137818 A303357 A251387 Adjacent sequences: A137814 A137815 A137816 * A137818 A137819 A137820 KEYWORD nonn AUTHOR R. K. Guy, R. J. Mathar and M. F. Hasler, Feb 11 2008 STATUS approved

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Last modified February 2 16:39 EST 2023. Contains 360023 sequences. (Running on oeis4.)