A063137 Composite numbers not divisible by 2, 3 or 5 which contain their largest prime factor as a substring in base 2.

91, 343, 407, 493, 539, 637, 893, 1001, 1189, 1309, 1343, 1403, 1643, 1681, 1771, 1859, 1961, 2527, 2717, 2783, 3059, 3151, 3179, 3223, 3451, 3703, 3731, 3773, 3887, 4063, 4199, 4459, 4579, 4669, 4823, 4913, 4991, 5291, 5453, 5491, 5719

Offset: 1

Author

Robert G. Wilson v, Aug 08 2001

Keywords

• base
• nonn

Examples

			a(7)= 19 * 47= 893: '1101111101' contains '101111' (47) and 5 < 19.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A062238.

Programs

PARI

sub(a,b)=my(m=1<<(log(2*a+1)\log(2))-1);while(b>=a,if(bitand(b,m)==a,return(1));b>>=1);0
gpf(n)=n=factor(n)[,1];n[#n]
is(n)=gcd(n,30)==1&&!isprime(n)&&sub(gpf(n),n) \\ Charles R Greathouse IV, Dec 08 2011

Extensions

Edited by Frank Ellermann, Feb 08 2002