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 A118081 #16 Sep 23 2024 22:54:01 %S A118081 2,4,6,8,10,12,14,16,20,22,26,28,32,38 %N A118081 Even numbers that can't be represented as the sum of two odd composite numbers. %C A118081 Suggested by the familiar puzzle, "What is the largest even number that is not the sum of two odd composite numbers?" The sequence contains all even numbers that are not of the form (9+6k)+9, (9+6k)+25, or (9+6k)+35, where k is a nonnegative integer. %C A118081 If 1 is allowed as a composite number, then only the eight numbers in A046458 are not representable. - _T. D. Noe_, Jun 01 2008 %e A118081 38 is in the sequence because 38 == 2 (mod 3) and all even numbers congruent to 2 mod 3 larger than 38 can be expressed as the sum of odd composites (9+6k) and 35, where k is a nonnegative integer. %t A118081 ocn=Select[Range[3,37,2],!PrimeQ[#]&];s=Total/@Tuples[ocn,2];Complement[Range[2,38,2],s] (* _James C. McMahon_, Sep 23 2024 *) %K A118081 fini,full,nonn %O A118081 1,1 %A A118081 _Graeme McRae_, Apr 11 2006