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 A077017 a(1) = 2, a(n+1) = smallest positive integer divisible by the n-th prime that also has a nontrivial common divisor with a(n). 3

%I

%S 2,2,6,10,14,22,26,34,38,46,58,62,74,82,86,94,106,118,122,134,142,146,

%T 158,166,178,194,202,206,214,218,226,254,262,274,278,298,302,314,326,

%U 334,346,358,362,382,386,394,398,422,446,454,458,466,478,482,502,514

%N a(1) = 2, a(n+1) = smallest positive integer divisible by the n-th prime that also has a nontrivial common divisor with a(n).

%C Each term of the sequence is a solution of the equation sigma(x)=3*(x-phi(x)) (*) - the proof is easy. Does there exist a solution of (*) which is not in the sequence? - _Farideh Firoozbakht_, Apr 22 2006

%F a(n) = 2*prime(n) for n>2.

%F a(n)=2*prime(n-1) for n>2. - _Farideh Firoozbakht_, Apr 22 2006

%t Join[{2,2},2*Prime[Range[2,60]]] (* _Harvey P. Dale_, Feb 24 2013 *)

%K nonn,easy

%O 1,1

%A _Amarnath Murthy_, Oct 28 2002

%E Corrected and extended by _Dean Hickerson_, Jan 28 2003

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Last modified December 6 16:24 EST 2019. Contains 329808 sequences. (Running on oeis4.)