OFFSET
1,1
COMMENTS
Every 4th consecutive number is divisible by 4 = 2*2 and therefore is not sphenic, so a(n) does not exist for n >= 4.
LINKS
Wikipedia, Sphenic number
EXAMPLE
30 = 2*3*5 is the first spheric number, so a(1) = 30.
The first case of two consecutive sphenic numbers is 230 = 2*5*23 and 231 = 3*7*11, so a(2) = 230.
The first case of three is 1309 = 7*11*17, 1310 = 2*5*131, and 1311 = 3*19*23, so a(3) = 1309.
CROSSREFS
KEYWORD
nonn,fini,full
AUTHOR
Jonathan Sondow, Oct 17 2017
STATUS
approved