OFFSET
1,2
COMMENTS
Smallest term of this sequence not also in A075109 is 675, followed by 1125. - Alonso del Arte, Nov 22 2011
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, B16
LINKS
Zak Seidov, Table of n, a(n) for n = 1..10000
W. A. Sentance, Occurrences of consecutive odd powerful numbers, Amer. Math. Monthly, 88 (1981), 272-274.
FORMULA
It is not true that a(n) = A001694(2n-1).
Sum_{n>=1} 1/a(n) = (2/3) * Sum_{n>=1} 1/A001694(n) = 2*zeta(2)*zeta(3)/(3*zeta(6)) = (2/3) * A082695 = 1.2957309... - Amiram Eldar, Jun 23 2020
EXAMPLE
Consecutive-odd examples from Sentance: {25,27},{70225,70227},{189750625,189750627}
MATHEMATICA
Powerful[n_Integer] := (n ==1) || Min[Transpose[FactorInteger[n]][[2]]]>=2; Select[Range[5000], OddQ[ # ]&&Powerful[ # ]&] (* T. D. Noe, May 04 2006 *)
Join[{1}, Select[Range[3, 4301, 2], Min[FactorInteger[#][[All, 2]]]>1&]] (* Harvey P. Dale, Jan 08 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Jul 12 2001
EXTENSIONS
Checked by T. D. Noe, May 04 2006
STATUS
approved