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A173956 n-th primorial modulo n. 1

%I

%S 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 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 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 n-th primorial modulo n.

%C Very similar to A076998.

%C For all n, a(A013929(n)) != 0, and a(A005117(n)) = 0. - _Michel Marcus_, Sep 03 2013 and _Antti Karttunen_, Nov 20 2017

%H Antti Karttunen, <a href="/A173956/b173956.txt">Table of n, a(n) for n = 1..16384</a>

%F a(n) = A002110(n) mod n. - _Michel Marcus_, Sep 03 2013

%e a(9) = p(9)# mod 9 = 23# mod 9 = 2*3*5*7*11*13*17*19*23 mod 9 = 6.

%t Array[Mod[Product[Prime@ i, {i, #}], #] &, 91] (* _Michael De Vlieger_, Nov 20 2017 *)

%o (PARI) a(n) = prod(i=1, n, prime(i)) % n; \\ _Michel Marcus_, Sep 03 2013

%Y Cf. A002110, A005117 (the positions of zeros).

%Y Differs from A076998 for the first time at n=16, where a(16) = 10, while A076998(16) = 2.

%K easy,nonn

%O 1,4

%A _Carl R. White_, Mar 03 2010

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Last modified January 29 01:54 EST 2020. Contains 331328 sequences. (Running on oeis4.)