OFFSET
1,2
REFERENCES
Bellman, R. and Shapiro, H. N. "The Distribution of Squarefree Integers in Small Intervals." Duke Math. J. 21, 629-637, 1954.
Borwein, J. and Bailey, D. Mathematics by Experiment: Plausible Reasoning in the 21st Century. Natick, MA: A. K. Peters, 2003.
Hardy, G. H. and Wright, E. M. "The Number of Squarefree Numbers." Section 18.6 in An Introduction to the Theory of Numbers, 5th ed. Oxford, England: Clarendon Press, pp. 269-270, 1979.
LINKS
G. C. Greubel and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (first 1000 terms from Greubel)
Eric Weisstein's World of Mathematics, Squarefree.
FORMULA
MATHEMATICA
bad = Rest@ Union[# (# + 1)/2 &@ Range[19], Range[14]^2, # (3 # - 1)/2 &@ Range[11]]; Select[Range[200], {} == Intersection[bad, Divisors[#]] &] (* Giovanni Resta, Jun 13 2016 *)
PROG
(PARI) list(lim)=my(v=List()); forsquarefree(n=1, lim\1, fordiv(n, d, if((ispolygonal(d, 3) || ispolygonal(d, 5)) && d>1, next(2))); listput(v, n[1])); Vec(v); \\ Charles R Greathouse IV, Dec 24 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Jan 13 2006
EXTENSIONS
Corrected and extended by Giovanni Resta, Jun 13 2016
STATUS
approved