This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A063137 #12 May 13 2013 01:54:05 %S A063137 91,343,407,493,539,637,893,1001,1189,1309,1343,1403,1643,1681,1771, %T A063137 1859,1961,2527,2717,2783,3059,3151,3179,3223,3451,3703,3731,3773, %U A063137 3887,4063,4199,4459,4579,4669,4823,4913,4991,5291,5453,5491,5719 %N A063137 Composite numbers not divisible by 2, 3 or 5 which contain their largest prime factor as a substring in base 2. %H A063137 Charles R Greathouse IV, <a href="/A063137/b063137.txt">Table of n, a(n) for n = 1..10000</a> %e A063137 a(7)= 19 * 47= 893: '1101111101' contains '101111' (47) and 5 < 19. %o A063137 (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 %o A063137 gpf(n)=n=factor(n)[,1];n[#n] %o A063137 is(n)=gcd(n,30)==1&&!isprime(n)&&sub(gpf(n),n) \\ _Charles R Greathouse IV_, Dec 08 2011 %Y A063137 Cf. A062238. %K A063137 base,nonn %O A063137 1,1 %A A063137 _Robert G. Wilson v_, Aug 08 2001 %E A063137 Edited by _Frank Ellermann_, Feb 08 2002