A067758 Numbers k such that sigma(prime(k) - 1) == 0 (mod k).

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

Cf. A000203, A006093, A008332.

Sequence in context: A240042 A099615 A114618 * A357752 A304677 A214418

Adjacent sequences: A067755 A067756 A067757 * A067759 A067760 A067761

Keyword

nonn

Author

Benoit Cloitre, Feb 05 2002

Extensions

More terms from Klaus Brockhaus, Feb 07 2002

Status

approved