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 10 results.

A172512 Partial sums of A057429.

Original entry on oeis.org

2, 5, 10, 17, 28, 47, 76, 123, 196, 275, 388, 539, 696, 859, 1026, 1265, 1506, 1789, 2142, 2509, 2888, 3345, 4342, 5709, 8750, 18891, 33590, 61119, 110326, 187617, 272854, 379547, 539970, 743759, 1108048, 2100009, 3303802, 4971123, 8675176, 13467233, 28784460
Offset: 1

Views

Author

Jonathan Vos Post, Feb 05 2010

Keywords

Crossrefs

Cf. A057429.

Extensions

More terms from the data at A057429 added by Amiram Eldar, Oct 19 2024

A000043 Mersenne exponents: primes p such that 2^p - 1 is prime. Then 2^p - 1 is called a Mersenne prime.

Original entry on oeis.org

2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, 110503, 132049, 216091, 756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917, 20996011, 24036583, 25964951, 30402457, 32582657, 37156667, 42643801, 43112609, 57885161, 74207281
Offset: 1

Views

Author

Keywords

Comments

Equivalently, integers k such that 2^k - 1 is prime.
It is believed (but unproved) that this sequence is infinite. The data suggest that the number of terms up to exponent N is roughly K log N for some constant K.
Length of prime repunits in base 2.
The associated perfect number N=2^(p-1)*M(p) (=A019279*A000668=A000396), has 2p (=A061645) divisors with harmonic mean p (and geometric mean sqrt(N)). - Lekraj Beedassy, Aug 21 2004
In one of his first publications Euler found the numbers up to 31 but erroneously included 41 and 47.
Equals number of bits in binary expansion of n-th Mersenne prime (A117293). - Artur Jasinski, Feb 09 2007
Number of divisors of n-th even perfect number, divided by 2. Number of divisors of n-th even perfect number that are powers of 2. Number of divisors of n-th even perfect number that are multiples of n-th Mersenne prime A000668(n). - Omar E. Pol, Feb 24 2008
Number of divisors of n-th even superperfect number A061652(n). Numbers of divisors of n-th superperfect number A019279(n), assuming there are no odd superperfect numbers. - Omar E. Pol, Mar 01 2008
Differences between exponents when the even perfect numbers are represented as differences of powers of 2, for example: The 5th even perfect number is 33550336 = 2^25 - 2^12 then a(5)=25-12=13 (see A135655, A133033, A090748). - Omar E. Pol, Mar 01 2008
Number of 1's in binary expansion of n-th even perfect number (see A135650). Number of 1's in binary expansion of divisors of n-th even perfect number that are multiples of n-th Mersenne prime A000668(n) (see A135652, A135653, A135654, A135655). - Omar E. Pol, May 04 2008
Indices of the numbers A006516 that are also even perfect numbers. - Omar E. Pol, Aug 30 2008
Indices of Mersenne numbers A000225 that are also Mersenne primes A000668. - Omar E. Pol, Aug 31 2008
The (prime) number p appears in this sequence if and only if there is no prime q<2^p-1 such that the order of 2 modulo q equals p; a special case is that if p=4k+3 is prime and also q=2p+1 is prime then the order of 2 modulo q is p so p is not a term of this sequence. - Joerg Arndt, Jan 16 2011
Primes p such that sigma(2^p) - sigma(2^p-1) = 2^p-1. - Jaroslav Krizek, Aug 02 2013
Integers k such that every degree k irreducible polynomial over GF(2) is also primitive, i.e., has order 2^k-1. Equivalently, the integers k such that A001037(k) = A011260(k). - Geoffrey Critzer, Dec 08 2019
Conjecture: for k > 1, 2^k-1 is (a Mersenne) prime or k = 2^(2^m)+1 (is a Fermat number) if and only if (k-1)^(2^k-2) == 1 (mod (2^k-1)k^2). - Thomas Ordowski, Oct 05 2023
Conjecture: for p prime, 2^p-1 is (a Mersenne) prime or p = 2^(2^m)+1 (is a Fermat number) if and only if (p-1)^(2^p-2) == 1 (mod 2^p-1). - David Barina, Nov 25 2024
Already as of Dec. 2020, all exponents up to 10^8 had been verified, implying that 74207281, 77232917 and 82589933 are indeed the next three terms. As of today, all exponents up to 130439863 have been tested at least once, see the GIMPS Milestones Report. - M. F. Hasler, Apr 11 2025
On June 23. 2025 all exponents up to 74340751 have been verified, confirming that 74207281 is the exponent of the 49th Mersenne Prime. - Rodolfo Ruiz-Huidobro, Jun 23 2025

Examples

			Corresponding to the initial terms 2, 3, 5, 7, 13, 17, 19, 31 ... we get the Mersenne primes 2^2 - 1 = 3, 2^3 - 1 = 7, 2^5 - 1 = 31, 127, 8191, 131071, 524287, 2147483647, ... (see A000668).
		

References

  • T. M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, 1976, page 4.
  • J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.
  • Jan Gullberg, Mathematics from the Birth of Numbers, W. W. Norton & Co., NY & London, 1997, §3.2 Prime Numbers, p. 79.
  • R. K. Guy, Unsolved Problems in Number Theory, Section A3.
  • F. Lemmermeyer, Reciprocity Laws From Euler to Eisenstein, Springer-Verlag, 2000, p. 57.
  • Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 19.
  • Alfred S. Posamentier, Math Charmers, Tantalizing Tidbits for the Mind, Prometheus Books, NY, 2003, page 47.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, pages 132-134.
  • B. Tuckerman, The 24th Mersenne prime, Notices Amer. Math. Soc., 18 (Jun, 1971), Abstract 684-A15, p. 608.

Crossrefs

Cf. A000668 (Mersenne primes).
Cf. A028335 (integer lengths of Mersenne primes).
Cf. A000225 (Mersenne numbers).
Cf. A001348 (Mersenne numbers with n prime).

Programs

  • Mathematica
    MersennePrimeExponent[Range[48]] (* Eric W. Weisstein, Jul 17 2017; updated Oct 21 2024 *)
  • PARI
    isA000043(n) = isprime(2^n-1) \\ Michael B. Porter, Oct 28 2009
    
  • PARI
    is(n)=my(h=Mod(2,2^n-1)); for(i=1, n-2, h=2*h^2-1); h==0||n==2 \\ Lucas-Lehmer test for exponent e. - Joerg Arndt, Jan 16 2011, and Charles R Greathouse IV, Jun 05 2013
    forprime(e=2,5000,if(is(e),print1(e,", "))); /* terms < 5000 */
    
  • Python
    from sympy import isprime, prime
    for n in range(1,100):
        if isprime(2**prime(n)-1):
            print(prime(n), end=', ') # Stefano Spezia, Dec 06 2018

Formula

a(n) = log((1/2)*(1+sqrt(1+8*A000396(n))))/log(2). - Artur Jasinski, Sep 23 2008 (under the assumption there are no odd perfect numbers, Joerg Arndt, Feb 23 2014)
a(n) = A000005(A061652(n)). - Omar E. Pol, Aug 26 2009
a(n) = A000120(A000396(n)), assuming there are no odd perfect numbers. - Omar E. Pol, Oct 30 2013

Extensions

Also in the sequence: p = 74207281. - Charles R Greathouse IV, Jan 19 2016
Also in the sequence: p = 77232917. - Eric W. Weisstein, Jan 03 2018
Also in the sequence: p = 82589933. - Gord Palameta, Dec 21 2018
a(46) = 42643801 and a(47) = 43112609, whose ordinal positions in the sequence are now confirmed, communicated by Eric W. Weisstein, Apr 12 2018
a(48) = 57885161, whose ordinal position in the sequence is now confirmed, communicated by Benjamin Przybocki, Jan 05 2022
Also in the sequence: p = 136279841. - Eric W. Weisstein, Oct 21 2024
As of Jan 31 2025, 48 terms are known, and are shown in the DATA section. Four additional numbers are known to be in the sequence, namely 74207281, 77232917, 82589933, and 136279841, but they may not be the next terms. See the GIMP website for the latest information. - N. J. A. Sloane, Jan 31 2025

A066408 Numbers n such that the Eisenstein integer (1 - ω)^n - 1 has prime norm, where ω = -1/2 + sqrt(-3)/2.

Original entry on oeis.org

2, 5, 7, 11, 17, 19, 79, 163, 193, 239, 317, 353, 659, 709, 1049, 1103, 1759, 2029, 5153, 7541, 9049, 10453, 23743, 255361, 534827, 2237561, 2888387, 4043119
Offset: 1

Views

Author

Mike Oakes, Dec 24 2001

Keywords

Comments

Analog of Mersenne primes in Eisenstein integers.
The norm of a + b * ω is (a + b * ω) * (a + b * ω^2) = a^2 + a*b + b^2.
Indices for which the Eisenstein-Mersenne numbers are primes. The p-th Eisenstein-Mersenne number can be written as 3^p - Legendre(3, p) * 3^((p + 1)/2) + 1. Note the enormous gap between 23743 and 255361. A modified version of Chris Nash's PFGW program was used to find the last term. - Jeroen Doumen (doumen(AT)win.tue.nl), Oct 31 2002
Let q be the integer quaternion (3 + i + j + k)/2. Then q^n - 1 is a quaternion prime for these n; that is, the norm of q^n - 1 is a rational prime. - T. D. Noe, Feb 02 2005
The actual norms also belong to the class of Generalized Unique primes (see Links section), that is primes which have a period of expansion of 1/p (in some general, non-decimal system) that it shares with no other prime. - Serge Batalov, Mar 29 2014
Next term > 4400000. - Serge Batalov, Jun 20 2023

Examples

			For n = 7, (1 - ω)^7 - 1 has norm 2269, a prime.
Or, for p = 7, 3^7 + 3^4 + 1 = 2269, which is prime.
		

References

  • P. H. T. Beelen, Algebraic geometry and coding theory, Ph.D. Thesis, Eindhoven, The Netherlands, September 2001.
  • J. M. Doumen, Ph.D. Thesis, Eindhoven, The Netherlands, to appear.
  • Mike Oakes, posting to primenumbers(AT)yahoogroups.com, Dec 24 2001.

Crossrefs

The actual norms are in A066413.

Programs

  • Mathematica
    maxPi = 3000; primeNormQ[p_] := PrimeQ[1 + 3^p - 2*3^(p/2)*Cos[(p*Pi)/6]]; A066408 = {}; Do[ If[primeNormQ[p = Prime[k]], Print[p]; AppendTo[A066408, p]], {k, 1, maxPi}]; A066408 (* Jean-François Alcover, Oct 21 2011 *)
  • PARI
    print1("2, "); /*the only even member; it is special*/ forprime(n=3,2029,if(ispseudoprime(3^n-kronecker(3,n)*3^((n+1)/2)+1),print1(n, ", "))) \\ Serge Batalov, Mar 29 2014

Extensions

a(26) from Serge Batalov, Mar 29 2014
a(27) from Ryan Propper and Serge Batalov, Jun 18 2023
a(28) from Ryan Propper and Serge Batalov, Jun 20 2023
Corrected link to NMBRTHRY posting. - Serge Batalov, Apr 01 2014

A007670 Numbers n such that 2^n - 2^((n + 1)/2) + 1 is prime.

Original entry on oeis.org

3, 7, 47, 73, 79, 113, 151, 167, 239, 241, 353, 367, 457, 1367, 3041, 27529, 49207, 160423, 364289, 991961, 1203793, 1667321, 4792057
Offset: 1

Views

Author

Keywords

Comments

If A007670 is a proper subset of A057429, then 364289 & 991961 are the next two terms.

References

  • J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A006598.

Programs

Extensions

a(16)-a(18) from Robert G. Wilson v, Sep 07 2000
a(19)-a(23) from Serge Batalov, Jun 16 2020

A007671 Numbers n such that 2^n + 2^((n + 1)/2) + 1 is prime.

Original entry on oeis.org

1, 3, 5, 11, 19, 29, 157, 163, 283, 379, 997, 10141, 14699, 77291, 85237, 106693, 203789, 3704053
Offset: 1

Views

Author

Keywords

References

  • J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A057429.

Programs

Extensions

More terms from Robert G. Wilson v, Sep 07 2000
203789 found and proved prime by Mike Oakes, on Sep 28 2000.
a(18) from Serge Batalov, Jun 16 2020

A182300 Gaussian-Mersenne primes: primes of the form ((1+i)^p - 1)((1-i)^p - 1).

Original entry on oeis.org

5, 13, 41, 113, 2113, 525313, 536903681, 140737471578113, 9444732965601851473921, 604462909806215075725313, 10384593717069655112945804582584321, 2854495385411919762116496381035264358442074113
Offset: 1

Views

Author

Arkadiusz Wesolowski, Apr 23 2012

Keywords

Comments

See A057429 for the values of p.
Primes of the form q = 2^p +- 2^((p+1)/2) + 1. Note that q == 1 (mod p). - Thomas Ordowski, Apr 18 2019

References

  • John Brillhart et al., Factorizations of b^n +/- 1, b=2,3,5,6,7,10,12 up to high powers, Amer. Math. Soc., Providence RI, 1988, pp. xcvi+236.
  • R. K. Guy, Unsolved Problems in Number Theory, New York: Springer-Verlag, 1994, pp. 33-36.
  • Miriam Hausmann and Harold N. Shapiro, Perfect Ideals over the Gaussian Integers, Comm. Pure Appl. Math. 29 (1976), pp. 323-341.

Crossrefs

Programs

  • Mathematica
    lst = {}; Do[a = (1 + I)^n - 1; b = a*Conjugate[a]; If[PrimeQ[b], AppendTo[lst, b]], {n, 151}]; lst
    gmp[n_]:=Module[{x=(1+I)^n-1},x*Conjugate[x]]; Select[Table[gmp[n],{n,200}],PrimeQ] (* Harvey P. Dale, Apr 27 2016 *)

A027206 Numbers m such that (1+i)^m + i is a Gaussian prime.

Original entry on oeis.org

0, 1, 2, 3, 4, 6, 7, 8, 11, 14, 16, 19, 38, 47, 62, 79, 151, 163, 167, 214, 239, 254, 283, 367, 379, 1214, 1367, 2558, 4406, 8846, 14699, 49207, 77291, 160423, 172486, 221006, 432182, 1513678, 2515574
Offset: 1

Views

Author

Ed Pegg Jr, Aug 07 2002

Keywords

Comments

Equivalently, either (1+i)^m + i times its conjugate is an ordinary prime, or m == 2 (mod 4) and 2^(m/2) + (-1)^((m-2)/4) is an ordinary prime.
Let z = (1+i)^m + i. If z is not pure real or pure imaginary, then z is a Gaussian prime if the product of z and its conjugate is a rational prime. That product is 1 + 2^m + sin(m*Pi/4)*2^(1+m/2). z is imaginary when m=4k+2, in which case z has magnitude 2^(2k+1) + (-1)^k. These pure imaginary numbers are Gaussian primes when 2^(2k+1)-1 is a Mersenne prime and 2k+1 == 1 (mod 4); that is, when m is twice an odd number in A112633. - T. D. Noe, Mar 07 2011

Crossrefs

Programs

  • Mathematica
    Select[Range[0,30000], PrimeQ[(1+I)^#+I, GaussianIntegers->True]&]

Extensions

More terms from Mike Oakes, Aug 07 2002
Edited by Dean Hickerson, Aug 14 2002
0 prepended by T. D. Noe, Mar 07 2011

A088962 Values of n that generate Generalized Gaussian-Mersenne primes (see below).

Original entry on oeis.org

2, 3, 4, 5, 7, 9, 10, 11, 12, 14, 15, 18, 19, 21, 22, 26, 27, 29, 30, 33, 34, 35, 42, 45, 47, 49, 51, 54, 55, 58, 63, 65, 66, 69, 70, 73, 79, 85, 86, 87, 105, 106, 110, 111, 113, 114, 126, 129, 138, 147, 151, 157, 163, 167, 178, 186, 189, 217, 231, 239, 241, 242, 283
Offset: 1

Views

Author

Marc Chamberland, Oct 28 2003

Keywords

Crossrefs

Cf. A057429, A182300 (Gaussian-Mersenne primes).

Programs

  • Mathematica
    t = {}; Do[s = FullSimplify[Exp[2 Re[Log [Cyclotomic[n, (1 + I)/2]]]]]; If[PrimeQ[Numerator[s]], AppendTo[t, n]], {n, 100}]; t (* T. D. Noe, May 02 2012 *)

Formula

The numerator of the rational expression exp(2*Re(log(Phi_n((1+i)/2)))) is prime, where Phi_n is the n-th cyclotomic polynomial.

A103329 Numbers n such that (1+i)^n - i is a Gaussian prime.

Original entry on oeis.org

0, 3, 4, 5, 8, 10, 16, 26, 29, 34, 73, 113, 122, 157, 178, 241, 353, 457, 997, 1042, 3041, 4562, 6434, 8506, 10141, 19378, 19882, 22426, 27529
Offset: 1

Views

Author

T. D. Noe, Jan 31 2005

Keywords

Comments

Note that A027206 and A057429 treat Gaussian primes of a similar form. The remaining case, (1+i)^n + 1, is a Gaussian prime for n=1,2,3,4 only.
Let z = (1+i)^n - i. If z is not pure real or pure imaginary, then z is a Gaussian prime if the product of z and its conjugate is a rational prime. That product is 1 + 2^n - sin(n*Pi/4)*2^(1+n/2). z is real when n=1. z is imaginary when n=4k+2, in which case, z has magnitude 2^(2k+1) - (-1)^k. These pure imaginary numbers are Gaussian primes when 2^(2k+1)-1 is a Mersenne prime and 2k+1 = 3 (mod 4); that is, when n is twice an odd number in A112634. - T. D. Noe, Mar 07 2011

Crossrefs

Cf. A027206 ((1+i)^n + i is a Gaussian prime), A057429 ((1+i)^n - 1 is a Gaussian prime).

Programs

  • Mathematica
    fQ[n_] := PrimeQ[(1 + I)^n - I, GaussianIntegers -> True]; Select[ Range[0, 30000], fQ]

Extensions

a(25)-a(29) from Robert G. Wilson v, Mar 02 2011.
0 prepended by T. D. Noe, Mar 07 2011

A207040 Generalized Gaussian-Mersenne primes (see below).

Original entry on oeis.org

5, 13, 29, 37, 41, 61, 109, 113, 397, 1321, 1429, 1613, 2113, 14449, 26317, 246241, 279073, 312709, 525313, 4327489, 7416361, 29247661, 47392381, 107367629, 536903681, 1326700741, 40388473189, 118750098349, 275415303169, 415878438361, 1759217765581
Offset: 1

Views

Author

Arkadiusz Wesolowski, May 07 2012

Keywords

Crossrefs

Supersequence of A182300 (Gaussian-Mersenne primes). Cf. A088962, A057429.

Programs

  • Mathematica
    lst = {}; Do[s = Numerator@FullSimplify@Exp[2*Re@Log@Cyclotomic[n, (1 + I)/2]]; If[PrimeQ[s] && ! MemberQ[lst, s], AppendTo[lst, s]], {n, 2^7}]; Take[Sort[lst], 31]

Formula

The numerator of the rational expression exp(2*Re(log(Phi_n((1 + i)/2)))) is prime, where Phi_n is the n-th cyclotomic polynomial. See A088962 for the values of n that generate primes.
Showing 1-10 of 10 results.