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 A055009 #16 Oct 15 2013 22:30:50 %S A055009 434,104,44,176,2924,34256,83509,539081,254963216,14600541172, %T A055009 201346999808 %N A055009 Smallest composite number x such that sigma(x + prime(n)#) = sigma(x) + prime(n)#, where prime(n)# = A002110(n) and sigma is A000203. %C A055009 a(12) <= 14841476269604. a(13) <= 314064788156864. - _Donovan Johnson_, Mar 17 2013 %e A055009 a(7) = 83509 = 37*37*61, sigma(83509)+510510 = 87234+510510 = sigma(83509+510510) = sigma(594019) = 597744. %o A055009 (PARI) a(n)=my(P=prod(i=1,n,prime(i)),x=4); while(isprime(x) || sigma(x+P) != sigma(x)+P, x++); x \\ _Charles R Greathouse IV_, Feb 14 2013 %Y A055009 The prime solutions for particular sigma(x+primorial) = sigma(x)+primorial equations are in A049481-A049485. %Y A055009 A000203, A002110, A015913-A015917, A049902-A049905, A049481-A049485. %K A055009 more,nonn %O A055009 1,1 %A A055009 _Labos Elemer_, May 31 2000 %E A055009 a(9)-a(10) from _Donovan Johnson_, Oct 15 2008 %E A055009 a(11) from _Donovan Johnson_, Mar 08 2013