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 1-10 of 51 results. Next

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

Views

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.

A035359 Number of partitions-into-distinct-parts of n (A000009) is a prime.

Original entry on oeis.org

3, 4, 5, 7, 22, 70, 100, 495, 1247, 2072, 320397, 3335367, 16168775, 37472505, 52940251, 78840125, 81191852
Offset: 1

Views

Author

Keywords

Comments

No other terms below 10^8. - Max Alekseyev, Jul 10 2015

Examples

			From _Gus Wiseman_, Jan 13 2020: (Start)
Strict partitions of a(1) = 3 through a(4) = 7:
  (3)    (4)    (5)    (7)
  (2,1)  (3,1)  (3,2)  (4,3)
                (4,1)  (5,2)
                       (6,1)
                       (4,2,1)
(End)
		

Crossrefs

The non-strict version is A046063.
The version for powers of 2 instead of primes is A331022.
The version for factorizations instead of strict partitions is A330991.
The version for strict factorizations instead of strict partitions is A331201.

Programs

Extensions

More terms from Eric W. Weisstein
a(12) from Max Alekseyev, Jul 04 2009
a(13)-a(14) from Giovanni Resta, Jun 05 2015, Jun 11 2015
a(15)-a(17) from Max Alekseyev, Jul 10 2015

A330991 Positive integers whose number of factorizations into factors > 1 (A001055) is a prime number (A000040).

Original entry on oeis.org

4, 6, 8, 9, 10, 14, 15, 16, 21, 22, 24, 25, 26, 27, 30, 32, 33, 34, 35, 38, 39, 40, 42, 46, 49, 51, 54, 55, 56, 57, 58, 60, 62, 64, 65, 66, 69, 70, 74, 77, 78, 81, 82, 84, 85, 86, 87, 88, 90, 91, 93, 94, 95, 96, 102, 104, 105, 106, 110, 111, 114, 115, 118, 119
Offset: 1

Views

Author

Gus Wiseman, Jan 07 2020

Keywords

Comments

In short, A001055(a(n)) belongs to A000040.

Examples

			Factorizations of selected terms:
  (4)    (8)      (16)       (24)       (60)       (96)
  (2*2)  (2*4)    (2*8)      (3*8)      (2*30)     (2*48)
         (2*2*2)  (4*4)      (4*6)      (3*20)     (3*32)
                  (2*2*4)    (2*12)     (4*15)     (4*24)
                  (2*2*2*2)  (2*2*6)    (5*12)     (6*16)
                             (2*3*4)    (6*10)     (8*12)
                             (2*2*2*3)  (2*5*6)    (2*6*8)
                                        (3*4*5)    (3*4*8)
                                        (2*2*15)   (4*4*6)
                                        (2*3*10)   (2*2*24)
                                        (2*2*3*5)  (2*3*16)
                                                   (2*4*12)
                                                   (2*2*3*8)
                                                   (2*2*4*6)
                                                   (2*3*4*4)
                                                   (2*2*2*12)
                                                   (2*2*2*2*6)
                                                   (2*2*2*3*4)
                                                   (2*2*2*2*2*3)
		

Crossrefs

Factorizations are A001055, with image A045782, with complement A330976.
Numbers whose number of strict integer partitions is prime are A035359.
Numbers whose number of integer partitions is prime are A046063.
Numbers whose number of set partitions is prime are A051130.
Numbers whose number of factorizations is a power of 2 are A330977.
The least number with prime(n) factorizations is A330992(n).

Programs

  • Mathematica
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    Select[Range[100],PrimeQ[Length[facs[#]]]&]

A052002 Numbers with an odd number of partitions.

Original entry on oeis.org

0, 1, 3, 4, 5, 6, 7, 12, 13, 14, 16, 17, 18, 20, 23, 24, 29, 32, 33, 35, 36, 37, 38, 39, 41, 43, 44, 48, 49, 51, 52, 53, 54, 56, 60, 61, 63, 67, 68, 69, 71, 72, 73, 76, 77, 81, 82, 83, 85, 87, 88, 89, 90, 91, 92, 93, 95, 99, 102, 104, 105, 107, 111, 114, 115, 118, 119, 121
Offset: 1

Views

Author

Patrick De Geest, Nov 15 1999

Keywords

Comments

A052003(n) = A000041(a(n+1)). - Reinhard Zumkeller, Nov 03 2015
Also, numbers having an odd number of partitions into distinct odd parts; that is, numbers m such that A000700(m) is odd. For example, 16 is in the list since 16 has 5 partitions into distinct odd parts, namely, 1 + 15, 3 + 13, 5 + 11, 7 + 9 and 1 + 3 + 5 + 7. See Formula section for a proof. - Peter Bala, Jan 22 2017

Examples

			From _Gus Wiseman_, Jan 13 2020: (Start)
The partitions of the initial terms are:
  (1)  (3)    (4)     (5)      (6)       (7)
       (21)   (22)    (32)     (33)      (43)
       (111)  (31)    (41)     (42)      (52)
              (211)   (221)    (51)      (61)
              (1111)  (311)    (222)     (322)
                      (2111)   (321)     (331)
                      (11111)  (411)     (421)
                               (2211)    (511)
                               (3111)    (2221)
                               (21111)   (3211)
                               (111111)  (4111)
                                         (22111)
                                         (31111)
                                         (211111)
                                         (1111111)
(End)
		

Crossrefs

The strict version is A001318, with complement A090864.
The version for prime instead of odd numbers is A046063.
The version for squarefree instead of odd numbers is A038630.
The version for set partitions appears to be A032766.
The version for factorizations is A331050.
The version for strict factorizations is A331230.

Programs

  • Haskell
    import Data.List (findIndices)
    a052002 n = a052002_list !! (n-1)
    a052002_list = findIndices odd a000041_list
    -- Reinhard Zumkeller, Nov 03 2015
  • Maple
    N:= 1000: # to get all terms <= N
    V:= Vector(N+1):
    V[1]:= 1:
    for i from 1 to (N+1)/2  do
      V[2*i..N+1]:= V[2*i..N+1] + V[1..N-2*i+2] mod 2
    od:
    select(t -> V[t+1]=1, [$1..N]); # Robert Israel, Jan 22 2017
  • Mathematica
    f[n_, k_] := Select[Range[250], Mod[PartitionsP[#], n] == k &]
    Table[f[2, k], {k, 0, 1}] (* Clark Kimberling, Jan 05 2014 *)
  • PARI
    for(n=0, 200, if(numbpart(n)%2==1, print1(n", "))) \\ Altug Alkan, Nov 02 2015
    

Formula

From Peter Bala, Jan 22 2016: (Start)
Sum_{n>=0} x^a(n) = (1 + x)*(1 + x^3)*(1 + x^5)*... taken modulo 2. Proof: Product_{n>=1} 1 + x^(2*n-1) = Product_{n>=1} (1 - x^(4*n-2))/(1 - x^(2*n-1)) = Product_{n>=1} (1 - x^(2*n))*(1 - x^(4*n-2))/( (1 - x^(2*n)) * (1 - x^(2*n-1)) ) = ( 1 + 2*Sum_{n>=1} (-1)^n*x^(2*n^2) )/(Product_{n>=1} (1 - x^n)) == 1/( Product_{n>=1} (1 - x^n) ) (mod 2). (End)

Extensions

Offset corrected and b-file adjusted by Reinhard Zumkeller, Nov 03 2015

A111036 Numbers n such that p(6n) is prime, where p(n) is the number of partitions of n.

Original entry on oeis.org

1, 6, 22, 28, 31, 36, 61, 83, 91, 181, 216, 263, 356, 417, 418, 428, 528, 557, 777, 1133, 1243, 1408, 2170, 2708, 3046, 3867, 5100, 5540, 5662, 7418, 9397, 12110, 12797, 14787, 16161, 16482, 18022, 19431, 19667, 21180, 22011, 22720, 23560, 27903
Offset: 1

Views

Author

Parthasarathy Nambi, Nov 11 2005

Keywords

Examples

			If n=91 then p(6n) = 27833079238879849385687 (prime).
		

Crossrefs

Programs

Extensions

a(10)-a(45) from Robert G. Wilson v, Nov 14 2005

A111045 Numbers n such that P(4n) is prime, where P(m) is the number of partitions of m.

Original entry on oeis.org

1, 9, 33, 42, 47, 53, 54, 110, 324, 534, 627, 642, 683, 728, 792, 1114, 2112, 2228, 2323, 2770, 3007, 3255, 3368, 3760, 4062, 4569, 6139, 7650, 7939, 8138, 8310, 8493, 8674, 9122, 9407, 10345, 11127, 13343, 14713, 15442, 15632, 16358, 16904, 18165, 19303
Offset: 1

Views

Author

Parthasarathy Nambi, Nov 11 2005

Keywords

Examples

			If n=110 then P(4*n) = 74878248419470886233 (prime).
		

Crossrefs

Programs

Extensions

a(9)-a(37) from Robert G. Wilson v, Nov 14 2005

A111389 Numbers n such that p(3n) is prime, where p(n) is the number of partitions of n.

Original entry on oeis.org

1, 2, 12, 44, 56, 62, 72, 122, 139, 166, 175, 182, 245, 251, 275, 362, 432, 526, 712, 831, 834, 836, 856, 909, 957, 1009, 1056, 1114, 1554, 2266, 2486, 2816, 3967, 4340, 5416, 6092, 6837, 6959, 7215, 7255, 7439, 7734, 9655, 10200, 11080, 11324, 11361, 12819
Offset: 1

Views

Author

Parthasarathy Nambi, Nov 09 2005

Keywords

Examples

			If n=72 then p(3n) = 15285151248481 (prime).
		

Crossrefs

Programs

Formula

Elements of A046063 which are == 0 (mod 3) divided by 3

Extensions

a(8)-a(48) from Robert G. Wilson v, Nov 11 2005

A114165 Numbers n such that p(2n) is prime, where p(n) is the number of partitions of n.

Original entry on oeis.org

1, 2, 3, 18, 66, 84, 93, 94, 106, 108, 151, 183, 220, 249, 273, 329, 543, 648, 789, 793, 1068, 1251, 1254, 1284, 1366, 1456, 1549, 1584, 1671, 1771, 2059, 2131, 2228, 2331, 2501, 3399, 3729, 4224, 4456, 4646, 4999, 5093, 5540, 6014, 6510, 6736, 7520, 8124
Offset: 1

Views

Author

Robert G. Wilson v, Nov 14 2005

Keywords

Comments

2n-th partition number (A000041(2n)) is prime.

Crossrefs

Programs

  • Mathematica
    Select[ Range[9137], PrimeQ[ PartitionsP[2# ]] &]
  • PARI
    is(n)=isprime(numbpart(2*n)) \\ Charles R Greathouse IV, Feb 17 2017

A114166 Numbers n such that p(5n) is prime, where p(n) is the number of partitions of n.

Original entry on oeis.org

1, 88, 105, 147, 165, 217, 1481, 2216, 2579, 2604, 3008, 3658, 3694, 4329, 4353, 4447, 4534, 5074, 5793, 6120, 6578, 6648, 7861, 7994, 8276, 8851, 9421, 10371, 12350, 12359, 12389, 13010, 13345, 13479, 14532, 14727, 16461, 19313, 19466, 20354
Offset: 1

Views

Author

Robert G. Wilson v, Nov 14 2005

Keywords

Crossrefs

Programs

  • Mathematica
    Select[ Range[20780], PrimeQ[PartitionsP[5# ]] &]
  • PARI
    is(n)=isprime(numbpart(5*n)) \\ Charles R Greathouse IV, Feb 17 2017

A114167 Numbers n such that p(7n) is prime, where p(n) is the number of partitions of n.

Original entry on oeis.org

11, 24, 75, 78, 94, 105, 155, 211, 293, 416, 506, 666, 1860, 3013, 3508, 3811, 4869, 5615, 5710, 8824, 8841, 8998, 10380, 11014, 11779, 13795, 14276, 15285, 18014, 19456, 19855, 22435, 23343, 23391, 26328, 30608, 31380, 32074, 32810, 33459
Offset: 1

Views

Author

Robert G. Wilson v, Nov 14 2005

Keywords

Crossrefs

Programs

  • Mathematica
    Select[ Range[28571], PrimeQ[PartitionsP[7# ]] &]
  • PARI
    is(n)=isprime(numbpart(7*n)) \\ Charles R Greathouse IV, Feb 17 2017
Showing 1-10 of 51 results. Next