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 A254755 Left-truncatable composites: every decimal suffix is a composite number. 6

%I

%S 4,6,8,9,14,16,18,24,26,28,34,36,38,39,44,46,48,49,54,56,58,64,66,68,

%T 69,74,76,78,84,86,88,94,96,98,99,104,106,108,114,116,118,124,126,128,

%U 134,136,138,144,146,148,154,156,158,164,166,168

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

%H Stanislav Sykora, <a href="/A254755/b254755.txt">Table of n, a(n) for n = 1..10000</a>

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

%o (PARI) isComposite(n) = (n>2)&&(!isprime(n));

%o 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);}

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

%K nonn,base

%O 1,1

%A _Stanislav Sykora_, Feb 15 2015

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Last modified January 16 21:37 EST 2019. Contains 319206 sequences. (Running on oeis4.)