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A067758
Numbers k such that sigma(prime(k) - 1) == 0 (mod k).
1
1, 4, 9, 27, 42, 60, 64, 70, 78, 144, 168, 180, 216, 238, 260, 318, 558, 600, 672, 960, 1008, 1053, 1260, 1620, 1806, 2112, 3318, 3780, 4608, 5544, 12152, 40084, 40095, 41664, 47040, 48825, 49176, 51870, 59832, 60528, 71040, 99008, 100356, 113904, 132000, 159000
OFFSET
1,2
COMMENTS
There are 91 terms up to and including 10 million. - Harvey P. Dale, Oct 04 2016
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..163 (terms 1..91 from Harvey P. Dale)
MATHEMATICA
Select[Range[120000], Divisible[DivisorSigma[1, Prime[#]-1], #]&] (* Harvey P. Dale, Oct 04 2016 *)
PROG
(PARI) for(k=1, 120000, if(sigma(prime(k)-1)%k==0, print1(k, ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 05 2002
EXTENSIONS
More terms from Klaus Brockhaus, Feb 07 2002
STATUS
approved