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 18 results. Next

A092759 a(n) = prime(n)^7.

Original entry on oeis.org

128, 2187, 78125, 823543, 19487171, 62748517, 410338673, 893871739, 3404825447, 17249876309, 27512614111, 94931877133, 194754273881, 271818611107, 506623120463, 1174711139837, 2488651484819, 3142742836021, 6060711605323
Offset: 1

Views

Author

Jorge Coveiro, Apr 13 2004

Keywords

Comments

Seventh powers of prime numbers. - Wesley Ivan Hurt, Mar 27 2014

Examples

			a(1) = 128 since the seventh power of the first prime is 2^7 = 128. - _Wesley Ivan Hurt_, Mar 27 2014
		

Crossrefs

Subsequence of A030626.

Programs

Formula

a(n) = A086874(n-1), n>1. - R. J. Mathar, Sep 08 2008
a(n) = A000040(n)^7 = A001015(A000040(n)). - Wesley Ivan Hurt, Mar 27 2014
Sum_{n>=1} 1/a(n) = P(7) = 0.0082838328... (A085967). - Amiram Eldar, Jul 27 2020
From Amiram Eldar, Jan 24 2021: (Start)
Product_{n>=1} (1 + 1/a(n)) = zeta(7)/zeta(14) = A013665/A013672.
Product_{n>=1} (1 - 1/a(n)) = 1/zeta(7) = 1/A013665. (End)

A085966 Decimal expansion of the prime zeta function at 6.

Original entry on oeis.org

0, 1, 7, 0, 7, 0, 0, 8, 6, 8, 5, 0, 6, 3, 6, 5, 1, 2, 9, 5, 4, 1, 3, 3, 6, 7, 3, 2, 6, 6, 0, 5, 9, 3, 9, 9, 2, 0, 9, 5, 8, 5, 9, 4, 1, 8, 7, 4, 5, 4, 4, 2, 4, 4, 7, 3, 3, 1, 6, 3, 3, 6, 8, 8, 3, 6, 9, 6, 9, 7, 3, 6, 7, 4, 7, 1, 7, 2, 4, 3, 6, 6, 7, 1, 8, 6, 0, 3, 5, 0, 0, 7, 8, 1, 8, 0, 6, 2, 3, 0, 2, 8, 8, 2, 3
Offset: 0

Views

Author

Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Jul 06 2003

Keywords

Comments

Mathar's Table 1 (cited below) lists expansions of the prime zeta function at integers s in 10..39. - Jason Kimberley, Jan 07 2017

Examples

			0.0170700868506365129541...
		

References

  • Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208-209.
  • J. W. L. Glaisher, On the Sums of Inverse Powers of the Prime Numbers, Quart. J. Math. 25, 347-362, 1891.

Crossrefs

Decimal expansion of the prime zeta function: A085548 (at 2), A085541 (at 3), A085964 (at 4), A085965 (at 5), this sequence (at 6), A085967 (at 7) to A085969 (at 9).

Programs

  • Magma
    R := RealField(106);
    PrimeZeta := func;
    [0]cat Reverse(IntegerToSequence(Floor(PrimeZeta(6,57)*10^105)));
    // Jason Kimberley, Dec 30 2016
    
  • Mathematica
    s[n_] := s[n] = Sum[ MoebiusMu[k]*Log[Zeta[6*k]]/k, {k, 1, n}] // RealDigits[#, 10, 104]& // First // Prepend[#, 0]&; s[100]; s[n = 200]; While[s[n] != s[n - 100], n = n + 100]; s[n] (* Jean-François Alcover, Feb 14 2013 *)
    RealDigits[ PrimeZetaP[ 6], 10, 111][[1]] (* Robert G. Wilson v, Sep 03 2014 *)
  • PARI
    sumeulerrat(1/p,6) \\ Hugo Pfoertner, Feb 03 2020

Formula

P(6) = Sum_{p prime} 1/p^6 = Sum_{n>=1} mobius(n)*log(zeta(6*n))/n
Equals 1/2^6 + A085995 + A086036. - R. J. Mathar, Jul 14 2012
Equals Sum_{k>=1} 1/A030516(k). - Amiram Eldar, Jul 27 2020

A085968 Decimal expansion of the prime zeta function at 8.

Original entry on oeis.org

0, 0, 4, 0, 6, 1, 4, 0, 5, 3, 6, 6, 5, 1, 7, 8, 3, 0, 5, 6, 0, 5, 2, 3, 4, 3, 9, 1, 4, 2, 6, 8, 3, 0, 8, 0, 5, 2, 2, 9, 7, 7, 1, 4, 4, 5, 1, 2, 0, 7, 1, 7, 4, 1, 0, 0, 1, 0, 3, 2, 6, 8, 8, 6, 8, 1, 7, 2, 8, 6, 3, 0, 4, 0, 7, 0, 7, 8, 8, 0, 4, 4, 0, 6, 0, 9, 2, 2, 8, 2, 8, 0, 5, 3, 0, 4, 3, 1, 3, 4, 4, 2, 6, 5, 6
Offset: 0

Views

Author

Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Jul 06 2003

Keywords

Comments

Mathar's Table 1 (cited below) lists expansions of the prime zeta function at integers s in 10..39. - Jason Kimberley, Jan 07 2017

Examples

			0.0040614053665178305605...
		

References

  • Henri Cohen, Number Theory, Volume II: Analytic and Modern Tools, GTM Vol. 240, Springer, 2007; see pp. 208-209.
  • J. W. L. Glaisher, On the Sums of Inverse Powers of the Prime Numbers, Quart. J. Math. 25, 347-362, 1891.

Crossrefs

Decimal expansion of the prime zeta function: A085548 (at 2), A085541 (at 3), A085964 (at 4) to A085967 (at 7), this sequence (at 8), A085969 (at 9).

Programs

  • Magma
    R := RealField(106);
    PrimeZeta := func;
    [0,0] cat Reverse(IntegerToSequence(Floor(PrimeZeta(8,43)*10^105)));
    // Jason Kimberley, Dec 30 2016
    
  • Mathematica
    s[n_] := s[n] = Sum[ MoebiusMu[k]*Log[Zeta[8*k]]/k, {k, 1, n}] // RealDigits[#, 10, 104]& // First // Prepend[#, 0]&; s[100]; s[n = 200]; While[s[n] != s[n - 100], n = n + 100]; s[n] (* Jean-François Alcover, Feb 14 2013 *)
    RealDigits[ PrimeZetaP[ 8], 10, 111][[1]] (* Robert G. Wilson v, Sep 03 2014 *)
  • PARI
    sumeulerrat(1/p, 8) \\ Hugo Pfoertner, Feb 03 2020

Formula

P(8) = Sum_{p prime} 1/p^8 = Sum_{n>=1} mobius(n)*log(zeta(8*n))/n.
Equals Sum_{k>=1} 1/A179645(k). - Amiram Eldar, Jul 27 2020

A179646 Product of the 5th power of a prime and different distinct prime of the 2nd power (p^5*q^2).

Original entry on oeis.org

288, 800, 972, 1568, 3872, 5408, 6075, 9248, 11552, 11907, 12500, 16928, 26912, 28125, 29403, 30752, 41067, 43808, 53792, 59168, 67228, 70227, 70688, 87723, 89888, 111392, 119072, 128547, 143648, 151263, 153125, 161312, 170528, 199712
Offset: 1

Views

Author

Keywords

Comments

288=2^5*3^2, 800=2^5*5^2,..

Crossrefs

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={2,5}; Select[Range[200000], f]
  • PARI
    list(lim)=my(v=List(),t);forprime(p=2,(lim\4)^(1/5),t=p^5;forprime(q=2,sqrt(lim\t),if(p==q,next);listput(v,t*q^2)));vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 20 2011
    
  • Python
    from math import isqrt
    from sympy import primepi, primerange, integer_nthroot
    def A189988(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(isqrt(x//p**4)) for p in primerange(integer_nthroot(x,4)[0]+1))+primepi(integer_nthroot(x,6)[0])
        return bisection(f,n,n) # Chai Wah Wu, Feb 21 2025

Formula

Sum_{n>=1} 1/a(n) = P(2)*P(5) - P(7) = A085548 * A085965 - A085967 = 0.007886..., where P is the prime zeta function. - Amiram Eldar, Jul 06 2020

A179666 Products of the 4th power of a prime and a distinct prime of power 3 (p^4*q^3).

Original entry on oeis.org

432, 648, 2000, 5000, 5488, 10125, 16875, 19208, 21296, 27783, 35152, 64827, 78608, 107811, 109744, 117128, 177957, 194672, 214375, 228488, 300125, 390224, 395307, 397953, 476656, 555579, 668168, 771147, 810448, 831875
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={3,4}; Select[Range[10^6], f]
    With[{nn=40},Select[Flatten[{#[[1]]^4 #[[2]]^3,#[[1]]^3 #[[2]]^4}&/@ Subsets[ Prime[Range[nn]],{2}]]//Union,#<=16nn^3&]] (* Harvey P. Dale, Nov 15 2020 *)
  • PARI
    list(lim)=my(v=List(),t);forprime(p=2,(lim\8)^(1/4),t=p^4;forprime(q=2,(lim\t)^(1/3),if(p==q,next);listput(v,t*q^3)));vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 20 2011
    
  • Python
    from sympy import primepi, integer_nthroot, primerange
    def A179666(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(integer_nthroot(x//p**4,3)[0]) for p in primerange(integer_nthroot(x,4)[0]+1))+primepi(integer_nthroot(x,7)[0])
        return bisection(f,n,n) # Chai Wah Wu, Mar 27 2025

Formula

Sum_{n>=1} 1/a(n) = P(3)*P(4) - P(7) = A085541 * A085964 - A085967 = 0.005171..., where P is the prime zeta function. - Amiram Eldar, Jul 06 2020

A179689 Numbers with prime signature {7,2}, i.e., of form p^7*q^2 with p and q distinct primes.

Original entry on oeis.org

1152, 3200, 6272, 8748, 15488, 21632, 36992, 46208, 54675, 67712, 107163, 107648, 123008, 175232, 215168, 236672, 264627, 282752, 312500, 359552, 369603, 445568, 476288, 574592, 632043, 645248, 682112, 703125, 789507, 798848, 881792, 1013888
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; local k;
          for k from 1+ `if` (n=1, 1, a(n-1))
            while sort (map (x-> x[2], ifactors(k)[2]), `>`)<>[7, 2]
          do od; k
        end:
    seq (a(n), n=1..32);  # Alois P. Heinz, Jan 23 2011
  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={2,7}; Select[Range[10^6], f]
  • PARI
    list(lim)=my(v=List(),t);forprime(p=2, (lim\4)^(1/7), t=p^7;forprime(q=2, sqrt(lim\t), if(p==q, next);listput(v,t*q^2))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 20 2011
    
  • Python
    from math import isqrt
    from sympy import primepi, integer_nthroot, primerange
    def A179689(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(isqrt(x//p**7)) for p in primerange(integer_nthroot(x,7)[0]+1))+primepi(integer_nthroot(x,9)[0])
        return bisection(f,n,n) # Chai Wah Wu, Feb 21 2025

Formula

Sum_{n>=1} 1/a(n) = P(2)*P(7) - P(9) = A085548 * A085967 - A085969 = 0.001741..., where P is the prime zeta function. - Amiram Eldar, Jul 06 2020

Extensions

Title edited by Daniel Forgues, Jan 22 2011

A179695 Numbers of the form p^3*q^2*r^2 where p, q, and r are distinct primes.

Original entry on oeis.org

1800, 2700, 3528, 4500, 5292, 8712, 9800, 12168, 12348, 13068, 18252, 20808, 24200, 24500, 25992, 31212, 33075, 33800, 34300, 38088, 38988, 47432, 47916, 55125, 57132, 57800, 60500, 60552, 66248, 69192, 72200, 77175, 79092, 81675, 84500
Offset: 1

Views

Author

Keywords

Comments

Subsequence of A225228. - Reinhard Zumkeller, May 03 2013

Crossrefs

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={2,2,3}; Select[Range[10^5], f]
    f[n_]:={Times@@(n^{2,2,3}),Times@@(n^{2,3,2}),Times@@(n^{3,2,2})}; Module[ {nn=20},Select[Flatten[f/@Subsets[Prime[Range[nn]],{3}]],#<= 72*Prime[ nn]^2&]]//Union (* Harvey P. Dale, Jul 05 2019 *)
  • PARI
    list(lim)=my(v=List(),t1,t2);forprime(p=2, (lim\36)^(1/3), t1=p^3;forprime(q=2, sqrt(lim\t1), if(p==q, next);t2=t1*q^2;forprime(r=q+1, sqrt(lim\t2), if(p==r,next);listput(v,t2*r^2)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 24 2011
    
  • Python
    from math import isqrt
    from sympy import primepi, primerange, integer_nthroot
    def A179695(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((t:=primepi(s:=isqrt(y:=isqrt(x//r**3))))+(t*(t-1)>>1)-sum(primepi(y//k) for k in primerange(1, s+1)) for r in primerange(integer_nthroot(x,3)[0]+1))+sum(primepi(isqrt(x//p**5)) for p in primerange(integer_nthroot(x,5)[0]+1))-primepi(integer_nthroot(x,7)[0])
        return bisection(f,n,n) # Chai Wah Wu, Mar 27 2025

Formula

A050326(a(n)) = 5. - Reinhard Zumkeller, May 03 2013
Sum_{n>=1} 1/a(n) = P(2)^2*P(3)/2 - P(3)*P(4)/2 - P(2)*P(5) + P(7) = 0.0032578591481263202818..., where P is the prime zeta function. - Amiram Eldar, Mar 07 2024

A190115 Numbers with prime factorization p^2*q^3*r^4 where p, q, and r are distinct primes.

Original entry on oeis.org

10800, 16200, 18000, 21168, 31752, 40500, 45000, 49392, 52272, 67500, 73008, 78408, 98000, 109512, 111132, 124848, 137200, 155952, 172872, 187272, 191664, 228528, 233928, 242000, 245000, 259308, 316368, 338000, 342792, 363312, 415152
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={2,3,4};Select[Range[900000],f]
  • PARI
    list(lim)=my(v=List(),t1,t2);forprime(p=2, (lim\72)^(1/4), t1=p^4;forprime(q=2, (lim\t1)^(1/3), if(p==q, next);t2=t1*q^3;forprime(r=2, sqrt(lim\t2), if(p==r||q==r, next);listput(v,t2*r^2)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 24 2011
    
  • Python
    from math import isqrt
    from sympy import primepi, primerange, integer_nthroot
    def A190115(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(isqrt(x//(r**4*q**3))) for r in primerange(integer_nthroot(x,4)[0]+1) for q in primerange(integer_nthroot(x//r**4,3)[0]+1))+sum(primepi(integer_nthroot(x//p**5,4)[0]) for p in primerange(integer_nthroot(x,5)[0]+1))+sum(primepi(integer_nthroot(x//p**6,3)[0]) for p in primerange(integer_nthroot(x,6)[0]+1))+sum(primepi(isqrt(x//p**7)) for p in primerange(integer_nthroot(x,7)[0]+1))-(primepi(integer_nthroot(x,9)[0])<<1)
        return bisection(f,n,n) # Chai Wah Wu, Mar 27 2025

Formula

Sum_{n>=1} 1/a(n) = P(2)*P(3)*P(4) - P(2)*P(7) - P(3)*P(6) - P(4)*P(5) + 2*P(9) = 0.00061171477910848082277..., where P is the prime zeta function. - Amiram Eldar, Mar 07 2024

A190382 Numbers with prime factorization p^2*q^2*r^2*s^3 where p, q, r, and s are distinct primes.

Original entry on oeis.org

88200, 132300, 217800, 220500, 304200, 308700, 326700, 426888, 456300, 520200, 544500, 596232, 640332, 649800, 760500, 780300, 894348, 952200, 974700, 1019592, 1185800, 1197900, 1273608, 1300500, 1428300, 1472328, 1494108, 1513800
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={2,2,2,3};Select[Range[2000000],f]
  • PARI
    list(lim)=my(v=List(),t1,t2,t3); forprime(p=2,sqrtnint(lim\900, 3), t1=p^3; forprime(q=2,sqrtint(lim\(36*t1)), if(q==p, next); t2=q^2*t1; forprime(r=2,sqrtint(lim\(4*t2)), if(r==p || r==q, next); t3=r^2*t2; forprime(s=2,sqrtint(lim\t3), if(s==p || s==q || s==r, next); listput(v, t3*s^2))))); Set(v) \\ Charles R Greathouse IV, Aug 25 2016

Formula

Sum_{n>=1} 1/a(n) = (P(2)^3*P(3) - 3*P(2)^2*P(5) - 3*P(2)*P(3)*P(4) + 6*P(2)*P(7) + 2*P(3)*P(6) + 3*P(4)*P(5) - 6*P(9))/6 = 0.00010783911499432484110..., where P is the prime zeta function. - Amiram Eldar, Mar 07 2024

A190470 Numbers with prime factorization p^2*q^3*r^5 where p, q, and r are distinct primes.

Original entry on oeis.org

21600, 36000, 42336, 48600, 95256, 98784, 104544, 121500, 146016, 196000, 225000, 235224, 249696, 274400, 311904, 328536, 333396, 337500, 383328, 457056, 484000, 561816, 632736, 676000, 701784, 726624, 830304, 1028376, 1064800, 1156000
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    f[n_]:=Sort[Last/@FactorInteger[n]]=={2,3,5}; Select[Range[2500000],f] (*and*) lst={}; Do[If[k!=n && k!=m && n!=m, AppendTo[lst, Prime[k]^2*Prime[n]^3*Prime[m]^5]], {n,20}, {m,20}, {k,20}]; Take[Union@lst,60]
  • PARI
    list(lim)=my(v=List(),t1,t2);forprime(p=2, (lim\72)^(1/5), t1=p^5;forprime(q=2, (lim\t1)^(1/3), if(p==q, next);t2=t1*q^3;forprime(r=2, sqrt(lim\t2), if(p==r||q==r, next);listput(v,t2*r^2)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 24 2011

Formula

Sum_{n>=1} 1/a(n) = P(2)*P(3)*P(5) - P(2)*P(8) - P(3)*P(7) - P(5)^2 + 2*P(10) = 0.00025025315357155375895..., where P is the prime zeta function. - Amiram Eldar, Mar 07 2024
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