OFFSET
1,1
REFERENCES
David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Books, 1986, entry 44, p. 103.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Vincenzo Librandi)
FORMULA
a(n) = A049104(n) - 1. - Zak Seidov, Feb 11 2016
MATHEMATICA
Flatten[Position[Partition[Table[DivisorSigma[0, n], {n, 5000}], 2, 1], _?(# == {6, 6}&)]] (* Harvey P. Dale, Apr 09 2012 *)
PROG
(PARI) isok(n) = (numdiv(n) == 6) && (numdiv(n+1) == 6); \\ Michel Marcus, Feb 11 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved