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A079672
Numbers of the form (3^s+1)/(3^r+1) for s > 1, 1 <= r <= s-1.
3
7, 61, 73, 547, 4921, 703, 5905, 44287, 6481, 398581, 478297, 3587227, 512461, 58807, 32285041, 38742049, 530713, 290565367, 42521761, 2615088301, 373584043, 4780783, 3138105961, 23535794707, 43040161, 211822152361, 3472494301
OFFSET
1,1
COMMENTS
(b^s+1) / (b^r+1) is an integer iff s/r is odd. - Jose Brox (tautocrona(AT)terra.es), Dec 27 2005
PROG
(PARI) for(x=2, 26, for(y=1, x-1, if(Mod(2^x+1, 2^y+1), 0, print1((3^x+1)/(3^y+1)", ")))) \\ The Mod(2^x+1, 2^y+1) is not a bug, since the exponents do not depend on the base in which they are calculated.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jose R. Brox (tautocrona(AT)terra.es), Jan 25 2003
STATUS
approved