OFFSET
1,1
COMMENTS
Theorem 4 in Goldston-Graham-Pintz-Yildirim proves that a(n+1) = a(n) + 1 for infinitely many n. - Charles R Greathouse IV, Jul 17 2015, corrected by M. F. Hasler, Jul 17 2019
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
D. A. Goldston, S. W. Graham, J. Pintz, and C. Y. Yıldırım, Small gaps between almost primes, the parity problem, and some conjectures of Erdos on consecutive integers (2008)
Will Nicholes, Prime Signatures
MATHEMATICA
f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 1, 2}; Select[Range[4000], f]
PROG
(PARI) is(n)=vecsort(factor(n)[, 2])==[1, 1, 1, 2]~ \\ Charles R Greathouse IV, Jul 17 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, May 03 2011
EXTENSIONS
Definition reworded by M. F. Hasler, Jul 17 2019
STATUS
approved