A375526 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..882

EXAMPLE

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, ...

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

PROG

(PARI) a(n) = denominator(sum(i=1, n, 1/fromdigits(digits(prime(i)), 11))); \\ Michel Marcus, Aug 31 2024

CROSSREFS

Cf. A031216, A375525.

Sequence in context: A104561 A211211 A127482 * A372741 A118747 A377707

Adjacent sequences: A375523 A375524 A375525 * A375527 A375528 A375529

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane, Aug 30 2024

STATUS

approved