The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A254939 a(n) = (A099795(n)^-1 mod p)*A099795(n), where p = prime(n). 3

%I

%S 1,4,36,120,2520,277200,5045040,183783600,4655851200,80313433200,

%T 32607253879200,2743667504978400,58772246027695200,

%U 5038384364010597600,56517528952814529600,34089489546705963770400,7391221142626702144764000

%N a(n) = (A099795(n)^-1 mod p)*A099795(n), where p = prime(n).

%C The sequence lists the smallest nonnegative solutions z to the system of congruences z == 1 (mod p), z == 0 (mod v(p-1)), where p is a prime and v(p-1) = lcm(1,...,p-1).

%H Umberto Cerruti, <a href="/A254939/a254939.pdf">Il Teorema Cinese dei Resti</a> (in Italian), 2015. The sequence is on page 21.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ModularInverse.html">Modular Inverse</a>.

%F a(n) = A255010(n)*A099795(n).

%e 5045040 is the seventh term of the sequence because the modular inverse of A099795(7) mod A000040(7) is 7 and 7*A099795(7) = 7*720720 = 5045040.

%p with(numtheory): P:=proc(q) local a, n; a:=[];

%p for n from 1 to q do a:=[op(a),n]; if isprime(n+1) then

%p print(lcm(op(a))*(lcm(op(a))^(-1) mod (n+1))); fi;

%p od; end: P(10^3); # _Paolo P. Lava_, Feb 16 2015

%t r[k_] := LCM @@ Range[k]; u[k_] := PowerMod[r[k - 1], -1, k] r[k - 1]; Table[u[Prime[n]], {n, 1, 20}]

%o (MAGMA) [Modinv(Lcm([1..p-1]),p)*Lcm([1..p-1]): p in PrimesUpTo(60)];

%o (PARI) a099795(n) = lcm(vector(prime(n)-1, k, k));

%o a(n) = {my(m = a099795(n)); m*lift(1/Mod(m, prime(n)));} \\ _Michel Marcus_, Feb 13 2015

%Y Cf. A000040, A056604, A099795, A254924, A255010.

%K nonn

%O 1,2

%A _Bruno Berselli_, Feb 12 2015 - proposed by Umberto Cerruti (Department of Mathematics "Giuseppe Peano", University of Turin, Italy)

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 13 08:34 EDT 2020. Contains 336442 sequences. (Running on oeis4.)