A378679 a(n) = denominator(Sum_{k=1..n} 1/P(k)), where P(k) = A006530(k) is the greatest prime dividing k for k >= 2, and P(1) = 1.

1, 2, 6, 3, 15, 15, 105, 210, 70, 70, 770, 2310, 30030, 30030, 30030, 15015, 255255, 255255, 4849845, 4849845, 4849845, 4849845, 111546435, 37182145, 7436429, 7436429, 22309287, 22309287, 646969323, 3234846615, 100280245065, 200560490130, 200560490130, 200560490130

Offset

1,2

Comments

See A378678 for more details.

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Formula

a(n) | A034386(n).

Mathematica

Denominator@ Accumulate[Table[1/FactorInteger[n][[-1, 1]], {n, 1, 34}]]

Prog

(PARI) lista(nmax) = {my(s = 1); print1(1, ", "); for(n = 2, nmax, f = factor(n); s += 1/f[#f~, 1]; print1(denominator(s), ", ")); }

Crossrefs

Cf. A006530, A034386, A057155, A378678 (numerators).

Sequence in context: A372000 A121566 A056839 * A302033 A337643 A071301

Adjacent sequences: A378676 A378677 A378678 * A378680 A378681 A378685

Keyword

nonn,easy,frac,new

Author

Amiram Eldar, Dec 03 2024

Status

approved