OFFSET
1,1
REFERENCES
David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Books, 1986, p. 103.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Vincenzo Librandi)
FORMULA
a(n) = A049103(n)+1. - Zak Seidov, Feb 11 2016
MATHEMATICA
Flatten[Position[Partition[Table[DivisorSigma[0, n-1], {n, 5000}], 2, 1], _?(#=={6, 6} &)]] (* Vincenzo Librandi, Oct 21 2012 *)
PROG
(PARI) isok(n) = (numdiv(n) == 6) && (numdiv(n-1) == 6); \\ Michel Marcus, Feb 11 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved