A083555 Quotient of LCM of prime(n+1)-1 and prime(n)-1 and GCD of the same two numbers.

2, 2, 6, 15, 30, 12, 72, 99, 154, 210, 30, 90, 420, 483, 598, 754, 870, 110, 1155, 1260, 156, 1599, 1804, 132, 600, 2550, 2703, 2862, 756, 72, 4095, 4420, 4692, 5106, 5550, 650, 702, 6723, 7138, 7654, 8010, 342, 9120, 2352, 9702, 1155, 1295, 12543, 12882

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

a(n) = lcm(A006093(n+1), A006093(n))/gcd(A006093(n+1), A006093(n));

a(n) = A083554(n)/A058263(n).

a(n) = A051537(A006093(n+1), A006093(n)). - Robert Israel, Jun 11 2017

Example

n=25: prime(25)=97, prime(26)=101; a(25) = lcm(96,100)/gcd(96,100) = 2400/4 = 600.

Maple

P:= seq(ithprime(i), i=1..100):
seq(ilcm(P[i+1]-1, P[i]-1)/igcd(P[i+1]-1, P[i]-1), i=1..99); # Robert Israel, Jun 11 2017

Mathematica

f[x_] := Prime[x]-1 Table[LCM[f[w+1], f[w]]/GCD[f[w+1], f[w]], {w, 1, 128}]
(* Second program: *)
Table[Apply[LCM[#1, #2]/GCD[#1, #2] &, Prime[n + {1, 0}] - 1], {n, 49}] (* Michael De Vlieger, Jun 11 2017 *)

Prog

(PARI) first(n)=my(v=vector(n), p=2, k, g); forprime(q=3, , g=gcd(p-1, q-1); v[k++]=(p-1)*(q-1)/g^2; p=q; if(k==n, break)); v \\ Charles R Greathouse IV, Jun 11 2017

Crossrefs

Cf. A006093, A083538..A083554, A051537, A058263.

Sequence in context: A216242 A330798 A260687 * A233147 A336633 A001464

Adjacent sequences: A083552 A083553 A083554 * A083556 A083557 A083558

Keyword

nonn

Author

Labos Elemer, May 22 2003

Status

approved