cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A049575 Prime partition numbers.

Original entry on oeis.org

2, 3, 5, 7, 11, 101, 17977, 10619863, 6620830889, 80630964769, 228204732751, 1171432692373, 1398341745571, 10963707205259, 15285151248481, 10657331232548839, 790738119649411319, 18987964267331664557, 74878248419470886233, 1394313503224447816939
Offset: 1

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Author

Keywords

Crossrefs

Intersection of A000040 and A000041.
Cf. A038753, A065728. - Reinhard Zumkeller, Nov 03 2009

Programs

  • Mathematica
    lst={};Do[a=PartitionsP[n];If[PrimeQ[a],AppendTo[lst,a]],{n,2*6!}];lst (* Vladimir Joseph Stephan Orlovsky, Jun 14 2009 *)
    Select[PartitionsP[Range[1000]],PrimeQ] (* Harvey P. Dale, Mar 11 2013 *)
  • PARI
    for(n=0,10^3,my(p=numbpart(n));if(isprime(p),print1(p,", "))); \\ Joerg Arndt, May 09 2013

Formula

a(n) = A000041(A046063(n)) = A000040(A051143(n)). - M. F. Hasler, Oct 19 2008
A010051(a(n))*A167392(a(n)) = 1. - Reinhard Zumkeller, Nov 03 2009

Extensions

More terms from James Sellers and Christian G. Bower, Oct 15 1999.

A236107 Nonprimes whose divisors are partition numbers.

Original entry on oeis.org

1, 15, 22, 77
Offset: 1

Views

Author

Omar E. Pol, Jan 22 2014

Keywords

Comments

By definition all terms are partition numbers.
Conjecture: no terms exist beyond 77. - Jon E. Schoenfield, Feb 05 2014

Examples

			15 is in the sequence because 15 is a nonprime number and the divisors of 15 are 1, 3, 5, 15, which are also partition numbers.
		

Crossrefs

Programs

  • Mathematica
    nmax = 1000;
    pp = PartitionsP[Range[nmax]];
    selQ[n_] := Module[{dd = Divisors[n]}, Intersection[pp, dd] == dd];
    Select[Range[nmax], !PrimeQ[#] && selQ[#]&] (* Jean-François Alcover, Apr 09 2020 *)
Showing 1-2 of 2 results.