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 A193315 #27 Mar 16 2020 05:40:07 %S A193315 1,4,9,15,25,35,49,55,77,91,121,143,169,187,221,247,289,323,361,391, %T A193315 437,403,529,551,589,667,713,703,841,899,961,943,1073,1147,1189,1271, %U A193315 1369,1363,1517,1591,1681,1763,1849,1927,2021,1891,2209,2279,2257,2491,2537,2623,2809,2867,2881 %N A193315 Write 2n=j+q (j,q positive noncomposite numbers); j*q maximal; then a(n)=j*q. %C A193315 a(n) = A102084(n) for n > 0. [_Reinhard Zumkeller_, Aug 28 2011] %e A193315 At n=6, 2n=12; 12 = 1 + 11 = 7 + 5; 7*5 = maximal => j*q = 7*5 = 35. %p A193315 isA008578 := proc(n) if n = 1 then true ; elif isprime(n) then true; else false; end if; end proc: %p A193315 A193315 := proc(n) local mx,j,q ; mx := 0 ; for j from 1 to 2*n-1 do if isA008578(j) then q := 2*n-j ; if isA008578(q) then mx := max(mx,j*q) ; end if ; end if; end do: mx ; end proc: %p A193315 seq(A193315(n),n=1..60) ; # _R. J. Mathar_, Aug 28 2011 %o A193315 (Sage) %o A193315 def is_A008578(n): return n == 1 or is_prime(n) %o A193315 def A193315(n): return max((j*(2*n-j)) for j in [1]+prime_range(n+1) if is_A008578(2*n-j)) %o A193315 [A193315(i) for i in range(1,15)] %o A193315 # _D. S. McNeil_, Aug 27 2011 %o A193315 (Haskell) %o A193315 a193315 1 = 1 %o A193315 a193315 n = maximum $ zipWith (*) prims $ map (a061397 . (2*n -)) prims %o A193315 where prims = takeWhile (<= n) a008578_list %o A193315 -- _Reinhard Zumkeller_, Aug 28 2011 %Y A193315 Cf. A073046, A008578, A061397. %K A193315 nonn %O A193315 1,2 %A A193315 _Juri-Stepan Gerasimov_, Aug 26 2011