

A077017


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


3



2, 2, 6, 10, 14, 22, 26, 34, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 134, 142, 146, 158, 166, 178, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 382, 386, 394, 398, 422, 446, 454, 458, 466, 478, 482, 502, 514
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

Each term of the sequence is a solution of the equation sigma(x)=3*(xphi(x)) (*)  the proof is easy. Does there exist a solution of (*) which is not in the sequence?  Farideh Firoozbakht, Apr 22 2006


LINKS

Table of n, a(n) for n=1..56.


FORMULA

a(n) = 2*prime(n) for n>2.
a(n)=2*prime(n1) for n>2.  Farideh Firoozbakht, Apr 22 2006


MATHEMATICA

Join[{2, 2}, 2*Prime[Range[2, 60]]] (* Harvey P. Dale, Feb 24 2013 *)


CROSSREFS

Sequence in context: A197218 A080460 A080456 * A181551 A127404 A292037
Adjacent sequences: A077014 A077015 A077016 * A077018 A077019 A077020


KEYWORD

nonn,easy,changed


AUTHOR

Amarnath Murthy, Oct 28 2002


EXTENSIONS

Corrected and extended by Dean Hickerson, Jan 28 2003


STATUS

approved



