A250213 Number of distinct prime factors of A241601(n).

0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 2, 1, 2, 0, 2, 1, 1, 1, 3, 2, 2, 2, 3, 2, 2, 1, 2, 2, 4, 2, 2, 3, 3, 1, 3, 1, 3, 1, 1, 2, 3, 1, 3, 4, 5, 2, 2, 3, 1, 2, 4, 4, 4, 3, 4, 3, 5, 4, 2, 3, 3, 4, 5, 2, 3, 2, 4, 5, 5, 3, 3, 2, 5, 1, 5, 2, 4, 3, 2, 5, 3, 3, 2, 5, 3, 3, 4

Offset

0,12

Comments

a(n) = 0 iff n is in the set {0, 1, 2, 3, 4, 5, 6, 8, 10, 14};

a(n) = 1 iff n is in A250220.

Links

Table of n, a(n) for n=0..87.

Formula

a(n) = A001221(A241601(n)).

Mathematica

b[n_] := Numerator[BernoulliB[2 n]/(2 n)];
c[n_] := Numerator[SeriesCoefficient[Log[Tan[x]+1/Cos[x]], {x, 0, 2n+1}]];
a[0] = 0; a[n_] := PrimeNu[If[EvenQ[n], Abs[b[n/2]], c[(n-1)/2]]];
Table[a[n], {n, 0, 78}] (* Jean-François Alcover, Jul 04 2019 *)

Crossrefs

Cf. A001221, A241601, A249909, A250214, A250220.

Sequence in context: A369862 A218867 A295664 * A033794 A218856 A101665

Adjacent sequences: A250210 A250211 A250212 * A250214 A250215 A250216

Keyword

nonn

Author

Eric Chen, Dec 28 2014

Extensions

More terms from Jean-François Alcover, Jul 04 2019

More terms from Jinyuan Wang, Apr 02 2020

Status

approved