A375526 a(n) = denominator of Sum_{i=1..n} 1/A031216(i).
2, 6, 30, 210, 420, 420, 1260, 126, 3150, 97650, 830025, 6640200, 6640200, 312089400, 312089400, 9050592600, 72404740800, 4851117633600, 354131587252800, 4603710634286400, 4603710634286400, 197959557274315200, 15227658251870400, 1477082850431428800, 78285391072865726400
Offset: 1
Examples
The first few fractions are 1/2, 5/6, 31/30, 247/210, 529/420, 559/420, 1747/1260, 181/126, 4651/3150, 147331/97650, 1276726/830025, 10379813/6640200, 10527373/6640200, ...
Links
- Alois P. Heinz, Table of n, a(n) for n = 1..882
Programs
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Maple
b:= n-> (l-> add(l[i]*11^(i-1), i=1..nops(l)))(convert(ithprime(n),base,10)): g:= proc(n) option remember; `if`(n<1, 0, g(n-1)+1/b(n)) end: a:= n-> denom(g(n)): seq(a(n), n=1..25); # Alois P. Heinz, Aug 30 2024
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PARI
a(n) = denominator(sum(i=1, n, 1/fromdigits(digits(prime(i)), 11))); \\ Michel Marcus, Aug 31 2024