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.

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A324588 Heinz numbers of integer partitions of n into perfect squares (A001156).

Original entry on oeis.org

1, 2, 4, 7, 8, 14, 16, 23, 28, 32, 46, 49, 53, 56, 64, 92, 97, 98, 106, 112, 128, 151, 161, 184, 194, 196, 212, 224, 227, 256, 302, 311, 322, 343, 368, 371, 388, 392, 419, 424, 448, 454, 512, 529, 541, 604, 622, 644, 661, 679, 686, 736, 742, 776, 784, 827, 838
Offset: 1

Views

Author

Gus Wiseman, Mar 08 2019

Keywords

Comments

The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
Also products of elements of A011757.

Examples

			The sequence of terms together with their prime indices begins:
   1: {}
   2: {1}
   4: {1,1}
   7: {4}
   8: {1,1,1}
  14: {1,4}
  16: {1,1,1,1}
  23: {9}
  28: {1,1,4}
  32: {1,1,1,1,1}
  46: {1,9}
  49: {4,4}
  53: {16}
  56: {1,1,1,4}
  64: {1,1,1,1,1,1}
  92: {1,1,9}
  97: {25}
  98: {1,4,4}
		

Crossrefs

Programs

  • Mathematica
    Select[Range[100],And@@Cases[FactorInteger[#],{p_,_}:>IntegerQ[Sqrt[PrimePi[p]]]]&]

A325128 Numbers in whose prime factorization the exponent of prime(k) is less than k for all prime indices k.

Original entry on oeis.org

1, 3, 5, 7, 11, 13, 15, 17, 19, 21, 23, 25, 29, 31, 33, 35, 37, 39, 41, 43, 47, 49, 51, 53, 55, 57, 59, 61, 65, 67, 69, 71, 73, 75, 77, 79, 83, 85, 87, 89, 91, 93, 95, 97, 101, 103, 105, 107, 109, 111, 113, 115, 119, 121, 123, 127, 129, 131, 133, 137, 139, 141
Offset: 1

Views

Author

Gus Wiseman, Apr 01 2019

Keywords

Comments

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k), so these are Heinz numbers of integer partitions where each part k appears fewer than k times. Such partitions are counted by A087153.
The asymptotic density of this sequence is Product_{k>=1} (1 - 1/prime(k)^k) = 0.44070243286030291209... - Amiram Eldar, Feb 02 2021

Examples

			The sequence of terms together with their prime indices begins:
   1: {}
   3: {2}
   5: {3}
   7: {4}
  11: {5}
  13: {6}
  15: {2,3}
  17: {7}
  19: {8}
  21: {2,4}
  23: {9}
  25: {3,3}
  29: {10}
  31: {11}
  33: {2,5}
  35: {3,4}
  37: {12}
  39: {2,6}
  41: {13}
  43: {14}
  47: {15}
  49: {4,4}
		

Crossrefs

Programs

  • Mathematica
    Select[Range[100],And@@Cases[If[#==1,{},FactorInteger[#]],{p_,k_}:>k
    				

A133018 Partition number of n, raised to power n.

Original entry on oeis.org

1, 1, 4, 27, 625, 16807, 1771561, 170859375, 54875873536, 19683000000000, 17080198121677824, 16985107389382393856, 43439888521963583647921, 113809328043328941786781301, 667840509835890864312744140625, 4816039244598889571670527496421376
Offset: 0

Views

Author

Omar E. Pol, Oct 31 2007

Keywords

Examples

			a(6)=1771561 because the partition number of 6 is 11 and 11^6=1771561.
		

Crossrefs

Cf. A000312, A058694, A062457, A133032, A259373, A265094. Partition numbers: A000041.

Programs

Formula

a(n) = A000041(n)^n.
a(n) ~ exp(1/24 - 3/(4*Pi^2) - (72+Pi^2)*sqrt(n)/(24*sqrt(6)*Pi) + sqrt(2/3)*Pi*n^(3/2)) / (3^(n/2) * 4^n * n^n). - Vaclav Kotesovec, Jun 23 2015

Extensions

More terms from R. J. Mathar, Jan 13 2008
a(15) from James C. McMahon, Mar 10 2025

A325127 Numbers in whose prime factorization the exponent of prime(k) is greater than k for all prime indices k.

Original entry on oeis.org

1, 4, 8, 16, 27, 32, 64, 81, 108, 128, 216, 243, 256, 324, 432, 512, 625, 648, 729, 864, 972, 1024, 1296, 1728, 1944, 2048, 2187, 2500, 2592, 2916, 3125, 3456, 3888, 4096, 5000, 5184, 5832, 6561, 6912, 7776, 8192, 8748, 10000, 10368, 11664, 12500, 13824, 15552
Offset: 1

Views

Author

Gus Wiseman, Apr 01 2019

Keywords

Comments

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k), so these are Heinz numbers of integer partitions where each part k appears more than k times. Such partitions are counted by A115584.

Examples

			The sequence of terms together with their prime indices begins:
    1: {}
    4: {1,1}
    8: {1,1,1}
   16: {1,1,1,1}
   27: {2,2,2}
   32: {1,1,1,1,1}
   64: {1,1,1,1,1,1}
   81: {2,2,2,2}
  108: {1,1,2,2,2}
  128: {1,1,1,1,1,1,1}
  216: {1,1,1,2,2,2}
  243: {2,2,2,2,2}
  256: {1,1,1,1,1,1,1,1}
  324: {1,1,2,2,2,2}
  432: {1,1,1,1,2,2,2}
  512: {1,1,1,1,1,1,1,1,1}
  625: {3,3,3,3}
  648: {1,1,1,2,2,2,2}
  729: {2,2,2,2,2,2}
  864: {1,1,1,1,1,2,2,2}
  972: {1,1,2,2,2,2,2}
		

Crossrefs

Programs

  • Mathematica
    Select[Range[1000],And@@Cases[If[#==1,{},FactorInteger[#]],{p_,k_}:>k>PrimePi[p]]&]
    With[{k = 4}, m = Prime[k]^(k + 1); s = {}; Do[p = Prime[i]; AppendTo[s, Join[{1}, p^Range[i + 1, Floor[Log[p, m]]]]], {i, 1, k}]; Union @ Select[Times @@@ Tuples[s], # <= m &]] (* Amiram Eldar, Oct 24 2020 *)

Formula

Sum_{n>=1} 1/a(n) = Product_{k>=1} 1 + 1/(prime(k)^k * (prime(k)-1)) = 1.58661114052385082598.... - Amiram Eldar, Oct 24 2020

A319075 Square array T(n,k) read by antidiagonal upwards in which row n lists the n-th powers of primes, hence column k lists the powers of the k-th prime, n >= 0, k >= 1.

Original entry on oeis.org

1, 2, 1, 4, 3, 1, 8, 9, 5, 1, 16, 27, 25, 7, 1, 32, 81, 125, 49, 11, 1, 64, 243, 625, 343, 121, 13, 1, 128, 729, 3125, 2401, 1331, 169, 17, 1, 256, 2187, 15625, 16807, 14641, 2197, 289, 19, 1, 512, 6561, 78125, 117649, 161051, 28561, 4913, 361, 23, 1, 1024, 19683, 390625, 823543, 1771561, 371293
Offset: 0

Views

Author

Omar E. Pol, Sep 09 2018

Keywords

Comments

If n = p - 1 where p is prime, then row n lists the numbers with p divisors.
The partial sums of column k give the column k of A319076.

Examples

			The corner of the square array is as follows:
         A000079 A000244 A000351  A000420    A001020    A001022     A001026
A000012        1,      1,      1,       1,         1,         1,          1, ...
A000040        2,      3,      5,       7,        11,        13,         17, ...
A001248        4,      9,     25,      49,       121,       169,        289, ...
A030078        8,     27,    125,     343,      1331,      2197,       4913, ...
A030514       16,     81,    625,    2401,     14641,     28561,      83521, ...
A050997       32,    243,   3125,   16807,    161051,    371293,    1419857, ...
A030516       64,    729,  15625,  117649,   1771561,   4826809,   24137569, ...
A092759      128,   2187,  78125,  823543,  19487171,  62748517,  410338673, ...
A179645      256,   6561, 390625, 5764801, 214358881, 815730721, 6975757441, ...
...
		

Crossrefs

Other rows n: A030635 (n=16), A030637 (n=18), A137486 (n=22), A137492 (n=28), A139571 (n=30), A139572 (n=36), A139573 (n=40), A139574 (n=42), A139575 (n=46), A173533 (n=52), A183062 (n=58), A183085 (n=60), A261700 (n=100).
Main diagonal gives A093360.
Second diagonal gives A062457.
Third diagonal gives A197987.
Removing the 1's we have A182944/ A182945.

Programs

  • PARI
    T(n, k) = prime(k)^n;

Formula

T(n,k) = A000040(k)^n, n >= 0, k >= 1.

A324587 Heinz numbers of integer partitions of n into distinct perfect squares (A033461).

Original entry on oeis.org

1, 2, 7, 14, 23, 46, 53, 97, 106, 151, 161, 194, 227, 302, 311, 322, 371, 419, 454, 541, 622, 661, 679, 742, 827, 838, 1009, 1057, 1082, 1193, 1219, 1322, 1358, 1427, 1589, 1619, 1654, 1879, 2018, 2114, 2143, 2177, 2231, 2386, 2437, 2438, 2741, 2854, 2933
Offset: 1

Views

Author

Gus Wiseman, Mar 08 2019

Keywords

Comments

The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
Also products of distinct elements of A011757.

Examples

			The sequence of terms together with their prime indices begins:
    1: {}
    2: {1}
    7: {4}
   14: {1,4}
   23: {9}
   46: {1,9}
   53: {16}
   97: {25}
  106: {1,16}
  151: {36}
  161: {4,9}
  194: {1,25}
  227: {49}
  302: {1,36}
  311: {64}
  322: {1,4,9}
  371: {4,16}
  419: {81}
  454: {1,49}
  541: {100}
		

Crossrefs

Programs

  • Mathematica
    Select[Range[1000],And@@Cases[FactorInteger[#],{p_,k_}:>k==1&&IntegerQ[Sqrt[PrimePi[p]]]]&]

A062006 a(n) = prime(n)^n + 1.

Original entry on oeis.org

3, 10, 126, 2402, 161052, 4826810, 410338674, 16983563042, 1801152661464, 420707233300202, 25408476896404832, 6582952005840035282, 925103102315013629322, 73885357344138503765450, 12063348350820368238715344, 3876269050118516845397872322
Offset: 1

Views

Author

Jason Earls, Jun 27 2001

Keywords

Comments

Sum of the n-th powers of the divisors of the n-th prime. - Wesley Ivan Hurt, Jan 17 2016

References

  • D. M. Burton, Elementary Number Theory, Allyn and Bacon, Inc. Boston, MA, 1976, pp. 56.

Crossrefs

Equals A062457(n) + 1.

Programs

  • Magma
    [NthPrime(n)^n+1 : n in [1..20]]; // Vincenzo Librandi, Jun 24 2015
  • Maple
    A062006:=n->ithprime(n)^n+1: seq(A062006(n), n=1..20); # Wesley Ivan Hurt, Jan 18 2016
  • Mathematica
    Table[Prime[n]^n + 1, {n, 20}] (* Harvey P. Dale, Dec 23 2013 *)
  • PARI
    for(n=1,22,print1(prime(n)^n+1, ", "))
    
  • PARI
    for (n=1, 100, a=2, a=prime(n)^n + 1; write("b062006.txt", n, " ", a) ) \\ Harry J. Smith, Jul 29 2009
    

Formula

a(n) = prime(n)^n + 1.

A093360 a(n) = prime(n)^(n-1).

Original entry on oeis.org

1, 3, 25, 343, 14641, 371293, 24137569, 893871739, 78310985281, 14507145975869, 819628286980801, 177917621779460413, 22563490300366186081, 1718264124282290785243, 256666986187667409334369
Offset: 1

Views

Author

Jorge Coveiro, Apr 28 2004

Keywords

Comments

Main diagonal of A319075. - Omar E. Pol, Sep 10 2018

Crossrefs

Cf. A062457.

Programs

  • Maple
    seq(ithprime(x)^(x-1),x=1..20);
  • Mathematica
    Table[Prime[n]^(n-1),{n,20}] (* Harvey P. Dale, Jun 11 2014 *)
  • PARI
    a(n) = prime(n)^(n-1);
    vector(20, n, a(n)) \\ Michel Marcus, Sep 13 2018

A324200 a(n) = 2^(A000043(n)-1) * ((2^A059305(n)) - 1), where A059305 gives the prime index of the n-th Mersenne prime, while A000043 gives its exponent.

Original entry on oeis.org

6, 60, 32752, 137438953408
Offset: 1

Views

Author

Antti Karttunen, Feb 18 2019

Keywords

Comments

If there are no odd perfect numbers then these are the positions of zeros in A324185.
The next term has 314 digits:
11781361728633673532894774498354952494238773929196300355071513798753168641589311119865182769801300280680127783231251635087526446289021607771691249214388576215221396663491984443067742263787264024212477244347842938066577043117995647400274369612403653814737339068225047641453182709824206687753689912418253153056583680.

Crossrefs

Programs

Formula

a(n) = ((2^A000720(A000668(n)))-1) * 2^(A000043(n)-1) = ((2^A059305(n)) - 1) * 2^(A000043(n)-1).
If no odd perfect numbers exist, then a(n) = A243071(A000396(n)), and thus A007814(a(n)) = A007814(A000396(n)).

A087480 Sum of all the primes raised to their corresponding powers.

Original entry on oeis.org

2, 11, 136, 2537, 163588, 4990397, 415329070, 17398892111, 1818551553574, 422525784853775, 25831002681258606, 6608783008521293887, 931711885323534923208, 74817069229462038688657
Offset: 1

Views

Author

Andy Edwards (AndynGen(AT)aol.com), Sep 09 2003

Keywords

Examples

			a(4) = 2^1 + 3^2 + 5^3 + 7^4 = 2 + 9 + 125 + 2401 = 2537.
		

Crossrefs

Partial sums of A062457.

Programs

  • Maple
    ListTools:-PartialSums( [seq(ithprime(i)^i, i=1..100)]); # Robert Israel, Nov 09 2015
  • Mathematica
    a[1] = 2; a[n_] := a[n - 1] + Prime[n]^n; Table[a[n], {n, 15}] (* Carlos Eduardo Olivieri, Nov 09 2015 *)
    Accumulate[Table[Prime[n]^n,{n,20}]] (* Harvey P. Dale, May 11 2019 *)
  • PARI
    a(n) = sum(i=1, n, prime(i)^i); \\ Michel Marcus, Sep 05 2013

Formula

a(n) = a(n-1) + prime(n)^n where prime(n) is the n-th prime.

Extensions

Corrected and extended by Ray Chandler, Sep 14 2003
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