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 A173956 #23 May 14 2022 14:44:15
%S A173956 0,0,0,2,0,0,0,2,6,0,0,6,0,0,0,10,0,12,0,10,0,0,0,6,20,0,3,14,0,0,0,
%T A173956 22,0,0,0,6,0,0,0,30,0,0,0,22,30,0,0,18,21,40,0,26,0,30,0,42,0,0,0,30,
%U A173956 0,0,42,18,0,0,0,34,0,0,0,30,0,0,60,38,0,0,0,50,12,0,0,42,0,0,0,66,0,30,0
%N A173956 n-th primorial modulo n.
%C A173956 Very similar to A076998.
%C A173956 For all n, a(A013929(n)) != 0, and a(A005117(n)) = 0. - _Michel Marcus_, Sep 03 2013 and _Antti Karttunen_, Nov 20 2017
%H A173956 Antti Karttunen, <a href="/A173956/b173956.txt">Table of n, a(n) for n = 1..16384</a>
%F A173956 a(n) = A002110(n) mod n. - _Michel Marcus_, Sep 03 2013
%e A173956 a(9) = p(9)# mod 9 = 23# mod 9 = 2*3*5*7*11*13*17*19*23 mod 9 = 6.
%t A173956 Array[Mod[Product[Prime@ i, {i, #}], #] &, 91] (* _Michael De Vlieger_, Nov 20 2017 *)
%t A173956 Module[{nn=100,prlm},prlm=FoldList[Times,Prime[Range[nn]]];Mod[ #[[1]], #[[2]]]&/@ Thread[{prlm,Range[nn]}]] (* _Harvey P. Dale_, May 14 2022 *)
%o A173956 (PARI) a(n) = prod(i=1, n, prime(i)) % n; \\ _Michel Marcus_, Sep 03 2013
%Y A173956 Cf. A002110, A005117 (the positions of zeros).
%Y A173956 Differs from A076998 for the first time at n=16, where a(16) = 10, while A076998(16) = 2.
%K A173956 easy,nonn
%O A173956 1,4
%A A173956 _Carl R. White_, Mar 03 2010