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

1,1

Links

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

Example

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

Prog

(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); }

Crossrefs

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

Sequence in context: A285586 A118951 A262389 * A275624 A228019 A228020

Adjacent sequences: A254752 A254753 A254754 * A254756 A254757 A254758

Keyword

nonn,base

Author

Stanislav Sykora, Feb 15 2015

Status

approved