A085904 Numbers k such that k, k+1 and k+2 are 7-smooth, i.e., all prime divisors <= 7 (A002473).

1, 2, 3, 4, 5, 6, 7, 8, 14, 48

Offset: 1

Author

Amarnath Murthy, Jul 09 2003

Keywords

• nonn
• fini
• full

Comments

No more terms < 3*10^7. Probably no more terms. - David Wasserman, Feb 10 2005

No more terms < 2^180. - Donovan Johnson, Oct 10 2012

There are no further terms: see A003032 (and maybe A002072). - Don Reble, Mar 14 2019

Examples

			48 is a member as 48, 49 and 50 have all prime divisors <= 7.
		

Crossrefs

Cf. A002473.

Programs

PARI

mx=2^180+2; v=vector(4607193); c=0; for(e1=0, 180, x1=2^e1; for(e2=0, 113, x2=x1*3^e2; if(x2>mx, next(2)); for(e3=0, 77, x3=x2*5^e3; if(x3>mx, next(2)); for(e4=0, 64, x4=x3*7^e4; if(x4>mx, next(2)); c++; v[c]=x4)))); v=vecsort(v); for(i=1, 4607191, if(v[i+1]-v[i]==1, if(v[i+2]-v[i]==2, print1(v[i] ", ")))) /* Donovan Johnson, Oct 10 2012 */

Extensions

Offset corrected and missing term added by Donovan Johnson, Oct 10 2012