A202260 Right-truncatable composites: every decimal prefix is a composite number.

4, 6, 8, 9, 40, 42, 44, 45, 46, 48, 49, 60, 62, 63, 64, 65, 66, 68, 69, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 400, 402, 403, 404, 405, 406, 407, 408, 420, 422, 423, 424, 425, 426, 427, 428, 429, 440, 441, 442, 444, 445, 446, 447, 448

Offset

1,1

Comments

Subsequence of A202259.

Links

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

Prog

(PARI) isComposite(n) = (n>2)&&(!isprime(n));
isRightTruncatableComposite(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); } \\ Stanislav Sykora, Feb 15 2015

Crossrefs

Cf. A012883 (right-truncatable noncomposites), A202259 (right-truncatable nonprimes), A024770 (right-truncatable primes).

Cf. A254750, A254752, A254754, A254755 (left-truncatable composites).

Sequence in context: A099071 A156673 A073866 * A001744 A113624 A113591

Adjacent sequences: A202257 A202258 A202259 * A202261 A202262 A202263

Keyword

nonn,base

Author

Jaroslav Krizek, Dec 25 2011

Status

approved