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A083555
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Quotient of LCM of prime(n+1)-1 and prime(n)-1 and GCD of the same two numbers.
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9
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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
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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n=25: prime(25)=97, prime(26)=101; a(25) = lcm(96,100)/gcd(96,100) = 2400/4 = 600.
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MAPLE
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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
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MATHEMATICA
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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 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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