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 A145781 #29 Feb 20 2017 23:11:12 %S A145781 2,3,6,15,91,246,715,3535,21099,95995,175470,4468006,31516774, %T A145781 192339970,212951314,5138843466,76699112491,103728576730, %U A145781 3051100701874,14417674958635,245230361204214,2296196521511806,10940476546738414 %N A145781 Least m >= 0 which when added to primorial(n) yields a square. %H A145781 G. C. Greubel, <a href="/A145781/b145781.txt">Table of n, a(n) for n = 1..630</a> %H A145781 C. Aebi and G. Cairns, <a href="http://www.parabola.unsw.edu.au/vol45_no1/vol45_no1_1.pdf">Partitions of primes</a>, Parabola 45, Issue 1 (2009); see the table on p. 5. - _Jonathan Sondow_, Jun 21 2012 %F A145781 a(n) = A216144(n)^2 - A002110(n). - _Jonathan Sondow_, Sep 02 2012 %e A145781 a(1)= 4 - 2 = 2, a(2)= 9 - 2*3 = 3, a(3)= 36 - 2*3*5 = 6, a(4)= 225 - 2*3*5*7 = 15, and a(5)= 2401 - 2*3*5*7*11 = 91. %t A145781 (IntegerPart[Sqrt[#]]+1)^2-#&/@Rest[FoldList[Times,1,Prime[Range[30]]]] (* _Harvey P. Dale_, Jan 14 2011 *) %o A145781 (PARI) j=[];for (n=1,30,j=concat(j,(ceil(sqrt(prod(i=1,n,prime(i))))^2 -prod(i=1,n,prime(i)))));j %Y A145781 Cf. A002110, A216144, A215658, A215659. %K A145781 nonn %O A145781 1,1 %A A145781 _Alexander R. Povolotsky_, Oct 18 2008 %E A145781 Definition shortened and clarified by _Jonathan Sondow_, Sep 02 2012