A254755 Left-truncatable composites: every decimal suffix is a composite number.

4, 6, 8, 9, 14, 16, 18, 24, 26, 28, 34, 36, 38, 39, 44, 46, 48, 49, 54, 56, 58, 64, 66, 68, 69, 74, 76, 78, 84, 86, 88, 94, 96, 98, 99, 104, 106, 108, 114, 116, 118, 124, 126, 128, 134, 136, 138, 144, 146, 148, 154, 156, 158, 164, 166, 168

Offset: 1

Author

Stanislav Sykora, Feb 15 2015

Keywords

• nonn
• base

Examples

			549 is a member because 549, 49, and 9 are all composites.
		

Links

• Stanislav Sykora, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A103443 (left-truncatable primes), A202260 (right-truncatable composites), A254750.

Programs

PARI

isComposite(n) = (n>2)&&(!isprime(n));
isLeftTruncatableComposite(n,b=10) = {my(k=b);if(!isComposite(n),return(0););while(n\k>0,if(!isComposite(n%k),return(0););k*=b);return(1);}