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A186309
Numbers n having more than one representation as k*(1+phi(k)/2), where phi(k) is Euler's totient function.
0
36, 540, 39852, 75418035, 113570688, 120668856, 141963360, 150836070, 18826510275, 37653020550, 106746035772831, 213492071545662, 2906980416141000, 4360470624211500, 11118121391391372
OFFSET
1,1
COMMENTS
The computations were provided by Robert Israel from sci.math. He found no n that had three representations up to k < 10^6. It would be a challenge to find an n with three representations.
EXAMPLE
For 36, sum of the coprimes of 9 is 27, add to 9 to get 36; the sum of the coprimes of 12 is 24, add 12 to 24 to also get 36. The corresponding {a,b} for each term is listed at the sci.math reference.
CROSSREFS
Sequence in context: A134289 A329913 A200708 * A374499 A159656 A081447
KEYWORD
nonn
AUTHOR
J. M. Bergot, Feb 17 2011
EXTENSIONS
a(11)-a(15) from Donovan Johnson, Feb 21 2011
STATUS
approved