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A250213 Number of distinct prime factors of A241601(n). 1
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 (list; graph; refs; listen; history; text; internal format)
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: A071460 A218867 A295664 * A033794 A218856 A101665

Adjacent sequences:  A250210 A250211 A250212 * A250214 A250215 A250216

KEYWORD

nonn,changed

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

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Last modified April 6 18:49 EDT 2020. Contains 333286 sequences. (Running on oeis4.)