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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A183062 Numbers with 59 divisors.

Original entry on oeis.org

288230376151711744, 4710128697246244834921603689, 34694469519536141888238489627838134765625, 10367793076318844190248738727596255138212949486449
Offset: 1

Views

Author

Omar E. Pol, Jul 31 2011

Keywords

Comments

Also, 58th powers of primes.
The n-th number with p divisors is equal to the n-th prime raised to power p-1, where p is prime.

Crossrefs

Programs

Formula

a(n) = A000040(n)^(59-1) = A000040(n)^58.
A000005(a(n)) = 59.

A183085 Numbers with 61 divisors.

Original entry on oeis.org

1152921504606846976, 42391158275216203514294433201, 867361737988403547205962240695953369140625, 508021860739623365322188197652216501772434524836001
Offset: 1

Views

Author

Omar E. Pol, Jul 31 2011

Keywords

Comments

Also, 60th powers of primes.
The n-th number with p divisors is equal to the n-th prime raised to power p-1, where p is prime.

Crossrefs

Programs

  • PARI
    a(n)=prime(n)^60

Formula

a(n) = A000040(n)^(61-1) = A000040(n)^60.
A000005(a(n)) = 61.

A351198 Sum of the 10th powers of the primes dividing n.

Original entry on oeis.org

0, 1024, 59049, 1024, 9765625, 60073, 282475249, 1024, 59049, 9766649, 25937424601, 60073, 137858491849, 282476273, 9824674, 1024, 2015993900449, 60073, 6131066257801, 9766649, 282534298, 25937425625, 41426511213649, 60073, 9765625, 137858492873, 59049, 282476273
Offset: 1

Views

Author

Wesley Ivan Hurt, Feb 04 2022

Keywords

Comments

Inverse Möbius transform of n^10 * c(n), where c(n) is the prime characteristic (A010051). - Wesley Ivan Hurt, Jun 22 2024

Crossrefs

Sum of the k-th powers of the primes dividing n for k=0..10 : A001221 (k=0), A008472 (k=1), A005063 (k=2), A005064 (k=3), A005065 (k=4), A351193 (k=5), A351194 (k=6), A351195 (k=7), A351196 (k=8), A351197 (k=9), this sequence (k=10).
Cf. A010051, A030629 (p^10).

Programs

  • Mathematica
    Array[DivisorSum[#, #^10 &, PrimeQ] &, 50]
    f[p_, e_] := p^10; a[n_] := Plus @@ f @@@ FactorInteger[n]; a[1] = 0; Array[a, 100] (* Amiram Eldar, Jun 20 2022 *)
  • PARI
    a(n) = vecsum(apply(x->x^10, factor(n)[, 1])); \\ Michel Marcus, Feb 05 2022
  • Python
    from sympy import primefactors
    def A351198(n): return sum(p**10 for p in primefactors(n)) # Chai Wah Wu, Feb 04 2022
    

Formula

a(n) = Sum_{p|n, p prime} p^10.
G.f.: Sum_{k>=1} prime(k)^10 * x^prime(k) / (1 - x^prime(k)). - Ilya Gutkovskiy, Feb 16 2022
Additive with a(p^e) = p^10. - Amiram Eldar, Jun 20 2022
a(n) = Sum_{d|n} d^10 * c(d), where c = A010051. - Wesley Ivan Hurt, Jun 22 2024

A189982 Numbers with prime signature (2,1,1,1), i.e., factorization p*q*r*s^2 with distinct primes p, q, r, s.

Original entry on oeis.org

420, 630, 660, 780, 924, 990, 1020, 1050, 1092, 1140, 1170, 1380, 1386, 1428, 1470, 1530, 1540, 1596, 1638, 1650, 1710, 1716, 1740, 1820, 1860, 1932, 1950, 2070, 2142, 2220, 2244, 2380, 2394, 2436, 2460, 2508, 2550, 2574, 2580, 2604, 2610, 2652, 2660, 2790
Offset: 1

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Author

Keywords

Comments

Theorem 4 in Goldston-Graham-Pintz-Yildirim proves that a(n+1) = a(n) + 1 for infinitely many n. - Charles R Greathouse IV, Jul 17 2015, corrected by M. F. Hasler, Jul 17 2019

Crossrefs

Part of the list A178739 .. A179696 and A030514 .. A030629, A189975 .. A189990 etc., cf. A101296.

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,1,2}; Select[Range[4000],f]
  • PARI
    is(n)=vecsort(factor(n)[,2])==[1, 1, 1, 2]~ \\ Charles R Greathouse IV, Jul 17 2015

Extensions

Definition reworded by M. F. Hasler, Jul 17 2019

A261700 Numbers with 101 divisors.

Original entry on oeis.org

1267650600228229401496703205376, 515377520732011331036461129765621272702107522001, 7888609052210118054117285652827862296732064351090230047702789306640625, 3234476509624757991344647769100216810857203198904625400933895331391691459636928060001
Offset: 1

Views

Author

Omar E. Pol, Aug 28 2015

Keywords

Comments

Also, 100th powers of primes.
The n-th number with p divisors is equal to the n-th prime raised to power p-1, where p is prime.

Examples

			a(1) = 2^100, a(2) = 3^100, a(3) = 5^100, a(4) = 7^100.
		

Crossrefs

Programs

Formula

a(n) = A000040(n)^(101-1) = A000040(n)^100.
A000005(a(n)) = 101.

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.

A179690 Numbers of the form p^2*q^2*r*s where p, q, r, and s are distinct primes.

Original entry on oeis.org

1260, 1980, 2100, 2340, 2772, 2940, 3060, 3150, 3276, 3300, 3420, 3900, 4140, 4284, 4410, 4788, 4950, 5100, 5148, 5220, 5580, 5700, 5796, 5850, 6468, 6660, 6732, 6900, 7260, 7308, 7350, 7380, 7524, 7644, 7650, 7700, 7740, 7812, 7956, 8460, 8550, 8700
Offset: 1

Views

Author

Keywords

Crossrefs

Part of the list A178739 .. A179696 and A030514 .. A030629, A189975 .. A189990 etc., cf. A101296. - M. F. Hasler, Jul 17 2019

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={1,1,2,2}; Select[Range[10000], f]
  • PARI
    list(lim)=my(v=List(),t1,t2,t3); forprime(p=2,sqrtint(lim\60), t1=p^2; forprime(q=2,sqrtint(lim\(6*t1)), if(q==p, next); t2=q^2*t1; forprime(r=2,lim\(2*t2), if(r==p || r==q, next); t3=r*t2; forprime(s=2,lim\t3, if(s==p || s==q || s==r, next); listput(v, t3*s))))); Set(v) \\ Charles R Greathouse IV, Aug 25 2016

A179691 Numbers p^5*q^2*r where p, q, r are 3 distinct primes.

Original entry on oeis.org

1440, 2016, 2400, 3168, 3744, 4704, 4860, 4896, 5472, 5600, 6624, 6804, 7840, 8352, 8800, 8928, 10400, 10656, 10692, 11616, 11808, 12150, 12384, 12636, 13536, 13600, 15200, 15264, 16224, 16524, 16992, 17248, 17568, 18400, 18468, 19296, 19360
Offset: 1

Views

Author

Keywords

Crossrefs

Part of the list A178739 .. A179696 (and A030514 .. A030629, A189982 .. A189990 etc, cf. A101296). - M. F. Hasler, Jul 17 2019
Subsequence of A175746 (numbers with 36 divisors).

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={1,2,5}; Select[Range[20000], f]
  • PARI
    list(lim)=my(v=List(),t1,t2);forprime(p=2, (lim\12)^(1/5), t1=p^5;forprime(q=2, sqrt(lim\t1), if(p==q, next);t2=t1*q^2;forprime(r=2, lim\t2, if(p==r||q==r, next);listput(v,t2*r)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 24 2011
    
  • Python
    from math import isqrt
    from sympy import primepi, primerange, integer_nthroot
    def A179691(n):
        def bisection(f,kmin=0,kmax=1):
            while f(kmax) > kmax: kmax <<= 1
            kmin = kmax >> 1
            while kmax-kmin > 1:
                kmid = kmax+kmin>>1
                if f(kmid) <= kmid:
                    kmax = kmid
                else:
                    kmin = kmid
            return kmax
        def f(x): return n+x-sum(primepi(x//(p**5*q**2)) for p in primerange(integer_nthroot(x,5)[0]+1) for q in primerange(isqrt(x//p**5)+1))+sum(primepi(integer_nthroot(x//p**5,3)[0]) for p in primerange(integer_nthroot(x,5)[0]+1))+sum(primepi(isqrt(x//p**6)) for p in primerange(integer_nthroot(x,6)[0]+1))+sum(primepi(x//p**7) for p in primerange(integer_nthroot(x,7)[0]+1))-(primepi(integer_nthroot(x,8)[0])<<1)
        return bisection(f,n,n) # Chai Wah Wu, Mar 27 2025

Extensions

Name improved by M. F. Hasler, Jul 17 2019

A166546 Natural numbers n such that d(n) + 1 is prime.

Original entry on oeis.org

1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 26, 27, 28, 29, 31, 32, 33, 34, 35, 37, 38, 39, 41, 43, 44, 45, 46, 47, 48, 50, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 63, 65, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 79, 80, 82, 83, 84, 85, 86, 87, 89, 90
Offset: 1

Views

Author

Giovanni Teofilatto, Oct 16 2009

Keywords

Comments

Natural numbers n such that d(d(n)+1)= 2. - Giovanni Teofilatto, Oct 26 2009
The complement is the union of A001248, A030514, A030516, A030626, A030627, A030629, A030631, A030632, A030633 etc. - R. J. Mathar, Oct 26 2009

Crossrefs

Cf. A000005.
Cf. A073915. - R. J. Mathar, Oct 26 2009

Programs

  • Magma
    [n: n in [1..100] | IsPrime(NumberOfDivisors(n)+1)]; // Vincenzo Librandi, Jan 20 2019
  • Mathematica
    Select[Range@90, PrimeQ[DivisorSigma[0, #] + 1] &] (* Vincenzo Librandi, Jan 20 2019 *)
  • PARI
    isok(n) = isprime(numdiv(n)+1); \\ Michel Marcus, Jan 20 2019
    

Formula

{1} U A000040 U A030513 U A030515 U A030628 U A030630 U A030634 U A030636 U A137485 U A137491 U A137493 U ... . - R. J. Mathar, Oct 26 2009

A280298 Numbers with 67 divisors.

Original entry on oeis.org

73786976294838206464, 30903154382632612361920641803529, 13552527156068805425093160010874271392822265625, 59768263894155949306790119265585619217025149412430681649, 539407797827634189900210968137750826278309533633974732577186113975161
Offset: 1

Views

Author

Omar E. Pol, Dec 31 2016

Keywords

Comments

Also, 66th powers of primes.
More generally, the n-th number with p divisors is equal to the n-th prime raised to power p-1, where p is prime. In this case, p = 67.

Examples

			a(1) = 2^66, a(2) = 3^66, a(3) = 5^66, a(4) = 7^66, a(5) = 11^66.
		

Crossrefs

Programs

  • Mathematica
    Array[Prime[#]^66 &, {5}] (* Michael De Vlieger, Dec 31 2016 *)
  • PARI
    a(n)=prime(n)^66

Formula

a(n) = A000040(n)^(67-1) = A000040(n)^66.
A000005(a(n)) = 67.
Previous Showing 11-20 of 39 results. Next