login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A250216 Weak irregular primes. A prime is weak irregular iff it is a Bernoulli irregular prime or a Euler irregular prime. 5
19, 31, 37, 43, 47, 59, 61, 67, 71, 79, 101, 103, 131, 137, 139, 149, 157, 193, 223, 233, 241, 251, 257, 263, 271, 277, 283, 293, 307, 311, 347, 349, 353, 359, 373, 379, 389, 401, 409, 419, 421, 433, 461, 463, 467, 491, 509, 523, 541, 547, 557, 563, 571, 577, 587, 593 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes p which divide A241601(k) for some k.

LINKS

Table of n, a(n) for n=1..56.

Peter Luschny, Irregular Bernoulli and Euler Primes.

The Prime Pages, Irregular Primes

The Prime Pages, Euler Irregular

MATHEMATICA

pmax = 593; m0 = 200; dm = 100;

b[n_] := Numerator[BernoulliB[2 n]/(2 n)];

c[n_] := Numerator[SeriesCoefficient[Log[Tan[x]+1/Cos[x]], {x, 0, 2n+1}]];

(* a1 = A241601 *) a1[0] = 1; a1[n_] := a1[n] = If[EvenQ[n], b[n/2] // Abs, c[(n - 1)/2]];

f[m_] := f[m] = Module[{}, aa = Table[a1[n], {n, 0, m}]; okQ[p_] := AnyTrue[aa, Divisible[#, p] &]; Reap[For[p = 2, p <= pmax, p = NextPrime[p], If[okQ[p], Sow[p]]]][[2, 1]]];

f[m = m0]; f[m = m + dm];

While[Print["m = ", m]; f[m] != f[m - dm], m = m + dm];

A250216 = f[m] (* Jean-Fran├žois Alcover, Jul 23 2019 *)

CROSSREFS

Cf. A000928, A120337, A128197.

Sequence in context: A316678 A330275 A038672 * A125148 A214798 A040066

Adjacent sequences:  A250213 A250214 A250215 * A250217 A250218 A250219

KEYWORD

nonn

AUTHOR

Eric Chen, Dec 24 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 5 03:58 EDT 2020. Contains 333238 sequences. (Running on oeis4.)