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 38 results. Next

A147641 Numbers B in the triples (A,B,C) that set a record in the L-function of the ABC conjecture if the search for C admits only the restricted integer subset of A009967 as described in A147642.

Original entry on oeis.org

16, 512, 12005, 6436341
Offset: 1

Views

Author

Artur Jasinski, Nov 09 2008

Keywords

Comments

If the ABC conjecture is true this sequence is finite.
For numbers A for this case see A147643.

Crossrefs

A008472 Sum of the distinct primes dividing n.

Original entry on oeis.org

0, 2, 3, 2, 5, 5, 7, 2, 3, 7, 11, 5, 13, 9, 8, 2, 17, 5, 19, 7, 10, 13, 23, 5, 5, 15, 3, 9, 29, 10, 31, 2, 14, 19, 12, 5, 37, 21, 16, 7, 41, 12, 43, 13, 8, 25, 47, 5, 7, 7, 20, 15, 53, 5, 16, 9, 22, 31, 59, 10, 61, 33, 10, 2, 18, 16, 67, 19, 26, 14, 71, 5, 73
Offset: 1

Views

Author

Keywords

Comments

Sometimes called sopf(n).
Sum of primes dividing n (without repetition) (compare A001414).
Equals A051731 * A061397 = inverse Mobius transform of [0, 2, 3, 0, 5, 0, 7, ...]. - Gary W. Adamson, Feb 14 2008
Equals row sums of triangle A143535. - Gary W. Adamson, Aug 23 2008
a(n) = n if and only if n is prime. - Daniel Forgues, Mar 24 2009
a(n) = n is a new record if and only if n is prime. - Zak Seidov, Jun 27 2009
a(A001043(n)) = A191583(n);
For n > 0: a(A000079(n)) = 2, a(A000244(n)) = 3, a(A000351(n)) = 5, a(A000420(n)) = 7;
a(A006899(n)) <= 3; a(A003586(n)) = 5; a(A033846(n)) = 7; a(A033849(n)) = 8; a(A033847(n)) = 9; a(A033850(n)) = 10; a(A143207(n)) = 10. - Reinhard Zumkeller, Jun 28 2011
For n > 1: a(n) = Sum(A027748(n,k): 1 <= k <= A001221(n)). - Reinhard Zumkeller, Aug 27 2011
If n is the product of twin primes (A037074), a(n) = 2*sqrt(n+1) = sqrt(4n+4). - Wesley Ivan Hurt, Sep 07 2013
From Wilf A. Wilson, Jul 21 2017: (Start)
a(n) + 2, n > 2, is the number of maximal subsemigroups of the monoid of orientation-preserving or -reversing mappings on a set with n elements.
a(n) + 3, n > 2, is the number of maximal subsemigroups of the monoid of orientation-preserving or -reversing partial mappings on a set with n elements.
(End)
The smallest m such that a(m) = n, or 0 if no such number m exists is A064502(n). The only integers that are not in the sequence are 1, 4 and 6. - Bernard Schott, Feb 07 2022

Examples

			a(18) = 5 because 18 = 2 * 3^2 and 2 + 3 = 5.
a(19) = 19 because 19 is prime.
a(20) = 7 because 20 = 2^2 * 5 and 2 + 5 = 7.
		

Crossrefs

First difference of A024924.
Sum of the k-th powers of the primes dividing n for k=0..10 : A001221 (k=0), this sequence (k=1), A005063 (k=2), A005064 (k=3), A005065 (k=4), A351193 (k=5), A351194 (k=6), A351195 (k=7), this sequence (k=8), A351197 (k=9), A351198 (k=10).
Cf. A010051.

Programs

  • Haskell
    a008472 = sum . a027748_row  -- Reinhard Zumkeller, Mar 29 2012
    
  • Magma
    [n eq 1 select 0 else &+[p[1]: p in Factorization(n)]: n in [1..100]]; // Vincenzo Librandi, Jun 24 2017
    
  • Maple
    A008472 := n -> add(d, d = select(isprime, numtheory[divisors](n))):
    seq(A008472(i), i = 1..40); # Peter Luschny, Jan 31 2012
    A008472 := proc(n)
            add( d, d= numtheory[factorset](n)) ;
    end proc: # R. J. Mathar, Jul 08 2012
  • Mathematica
    Prepend[Array[Plus @@ First[Transpose[FactorInteger[#]]] &, 100, 2], 0]
    Join[{0}, Rest[Total[Transpose[FactorInteger[#]][[1]]]&/@Range[100]]] (* Harvey P. Dale, Jun 18 2012 *)
    (* Requires version 7.0+ *) Table[DivisorSum[n, # &, PrimeQ[#] &], {n, 75}] (* Alonso del Arte, Dec 13 2014 *)
    Table[Sum[p, {p, Select[Divisors[n], PrimeQ]}], {n, 1, 100}] (* Vaclav Kotesovec, May 20 2020 *)
  • PARI
    sopf(n) = local(fac=factor(n)); sum(i=1,matsize(fac)[1],fac[i,1])
    
  • PARI
    vector(100,n,vecsum(factor(n)[,1]~)) \\ Derek Orr, May 13 2015
    
  • PARI
    A008472(n)=vecsum(factor(n)[,1]) \\ M. F. Hasler, Jul 18 2015
    
  • Python
    from sympy import primefactors
    def A008472(n): return sum(primefactors(n)) # Chai Wah Wu, Feb 03 2022
  • Sage
    def A008472(n):
        return add(d for d in divisors(n) if is_prime(d))
    print([A008472(i) for i in (1..40)]) # Peter Luschny, Jan 31 2012
    
  • Sage
    [sum(prime_factors(n)) for n in range(1,74)] # Giuseppe Coppoletta, Jan 19 2015
    

Formula

Let n = Product_j prime(j)^k(j) where k(j) >= 1, then a(n) = Sum_j prime(j).
Additive with a(p^e) = p.
G.f.: Sum_{k >= 1} prime(k)*x^prime(k)/(1-x^prime(k)). - Franklin T. Adams-Watters, Sep 01 2009
L.g.f.: -log(Product_{k>=1} (1 - x^prime(k))) = Sum_{n>=1} a(n)*x^n/n. - Ilya Gutkovskiy, May 06 2017
Dirichlet g.f.: primezeta(s-1)*zeta(s). - Benedict W. J. Irwin, Jul 11 2018
a(n) = Sum_{p|n, p prime} p. - Wesley Ivan Hurt, Feb 04 2022
From Bernard Schott, Feb 07 2022: (Start)
For n > 0: a(A001020(n)) = 11, a(A001022(n)) = 13, a(A001026(n)) = 17, a(A001029(n)) = 19, a(A009967(n)) = 23, a(A009973(n)) = 29, a(A009975(n)) = 31, a(A009981(n)) = 37, a(A009985(n)) = 41, a(A009987(n)) = 43, a(A009991(n)) = 47.
For p odd prime, a(2*p) = p+2 <==> a(A100484(n)) = A052147(n) for n > 1. (End)
a(n) = Sum_{d|n} d * c(d), where c = A010051. - Wesley Ivan Hurt, Jun 22 2024

A153656 Triangle T(n, k) = T(n-1, k) + T(n-1, k-1) + (2*j +3)*prime(j)*T(n-2, k-1) with j=9, read by rows.

Original entry on oeis.org

2, 23, 23, 2, 1054, 2, 2, 12165, 12165, 2, 2, 13133, 533412, 13133, 2, 2, 14101, 6422240, 6422240, 14101, 2, 2, 15069, 12779580, 270482476, 12779580, 15069, 2, 2, 16037, 19605432, 3385203976, 3385203976, 19605432, 16037, 2, 2, 17005, 26899796, 9577346548, 137413443860, 9577346548, 26899796, 17005, 2
Offset: 1

Views

Author

Roger L. Bagula, Dec 30 2008

Keywords

Examples

			Triangle begins as:
   2;
  23,    23;
   2,  1054,        2;
   2, 12165,    12165,          2;
   2, 13133,   533412,      13133,            2;
   2, 14101,  6422240,    6422240,        14101,          2;
   2, 15069, 12779580,  270482476,     12779580,      15069,        2;
   2, 16037, 19605432, 3385203976,   3385203976,   19605432,    16037,     2;
   2, 17005, 26899796, 9577346548, 137413443860, 9577346548, 26899796, 17005, 2;
		

Crossrefs

Sequences with variable (p,q,j): A153516 (0,1,2), A153518 (0,1,3), A153520 (0,1,4), A153521 (0,1,5), A153648 (1,0,3), A153649 (1,1,4), A153650 (1,4,5), A153651 (1,5,6), A153652 (2,1,7), A153653 (2,1,8), A153654 (2,1,9), A153655 (2,1,10), this sequence (2,3,9), A153657 (2,7,10).
Cf. A009967 (powers of 23).

Programs

  • Magma
    f:= func< n,j | Round(((3-(-1)^n)/2)*NthPrime(j)^(n-1) - 2^((3-(-1)^n)/2)) >;
    function T(n,k,p,q,j)
      if n eq 2 then return NthPrime(j);
      elif (n eq 3 and k eq 2 or n eq 4 and k eq 2 or n eq 4 and k eq 3) then return f(n,j);
      elif (k eq 1 or k eq n) then return 2;
      else return T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*NthPrime(j)*T(n-2,k-1,p,q,j);
      end if; return T;
    end function;
    [T(n,k,2,3,9): k in [1..n], n in [1..12]]; // G. C. Greubel, Mar 06 2021
  • Mathematica
    T[n_, k_, p_, q_, j_]:= T[n,k,p,q,j]= If[n==2, Prime[j], If[n==3 && k==2 || n==4 && 2<=k<=3, ((3-(-1)^n)/2)*Prime[j]^(n-1) -2^((3-(-1)^n)/2), If[k==1 || k==n, 2, T[n-1,k,p,q,j] + T[n-1,k-1,p,q,j] + (p*j+q)*Prime[j]*T[n-2,k-1,p,q,j] ]]];
    Table[T[n,k,2,3,9], {n,12}, {k,n}]//Flatten (* modified by G. C. Greubel, Mar 06 2021 *)
  • Sage
    @CachedFunction
    def f(n,j): return ((3-(-1)^n)/2)*nth_prime(j)^(n-1) - 2^((3-(-1)^n)/2)
    def T(n,k,p,q,j):
        if (n==2): return nth_prime(j)
        elif (n==3 and k==2 or n==4 and 2<=k<=3): return f(n,j)
        elif (k==1 or k==n): return 2
        else: return T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*nth_prime(j)*T(n-2,k-1,p,q,j)
    flatten([[T(n,k,2,3,9) for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Mar 06 2021
    

Formula

T(n, k) = T(n-1, k) + T(n-1, k-1) + (2*j +3)*prime(j)*T(n-2, k-1) with j=9.
From G. C. Greubel, Mar 06 2021: (Start)
T(n,k,p,q,j) = T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*prime(j)*T(n-2,k-1,p,q,j) with T(2,k,p,q,j) = prime(j), T(3,2,p,q,j) = 2*prime(j)^2 -4, T(4,2,p,q,j) = T(4,3,p,q,j) = prime(j)^2 -2, T(n,1,p,q,j) = T(n,n,p,q,j) = 2 and (p,q,j) = (2,3,9).
Sum_{k=0..n} T(n,k,p,q,j) = 2*prime(j)^(n-1), for (p,q,j)=(2,3,9), = 2*A009967(n-1). (End)

Extensions

Edited by G. C. Greubel, Mar 06 2021

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.

A073215 Sum of two powers of 23.

Original entry on oeis.org

2, 24, 46, 530, 552, 1058, 12168, 12190, 12696, 24334, 279842, 279864, 280370, 292008, 559682, 6436344, 6436366, 6436872, 6448510, 6716184, 12872686, 148035890, 148035912, 148036418, 148048056, 148315730, 154472232, 296071778
Offset: 0

Views

Author

Jeremy Gardiner, Jul 20 2002

Keywords

Examples

			T(2,0) = 23^2 + 23^0 = 530.
Table begins:
       2;
      24,     46;
     530,    552,   1058;
   12168,  12190,  12696,  24334;
  279842, 279864, 280370, 292008, 559682;
  ...
		

Crossrefs

Cf. A009967.
Equals twice A072822.
Sums of two powers of n: A073423 (0), A007395 (1), A173786 (2), A055235 (3), A055236 (4), A055237 (5), A055257 (6), A055258 (7), A055259 (8), A055260 (9), A052216 (10), A073211 (11), A194887 (12), A072390 (13), A055261 (16), A073213 (17), A073214 (19).

Programs

  • Mathematica
    With[{nn=30},Take[Union[Total/@Tuples[23^Range[0,nn],2]],nn]] (* Harvey P. Dale, Oct 16 2017 *)
  • Python
    from math import isqrt
    def A073215(n): return 23**(a:=(k:=isqrt(m:=n<<1))+(m>k*(k+1))-1)+23**(n-1-(a*(a+1)>>1)) # Chai Wah Wu, Apr 09 2025

Formula

T(n, m) = 23^n + 23^m, for n >= 0 and m in [0..n].
Bivariate g.f.: (2 - 24*x) / ((1 - x) * (1 - 23*x) * (1 - 23*x*y)). - J. Douglas Morrison, Jul 29 2021

A147642 Numbers C which generate successive records of the merit function of the ABC conjecture admitting only C which are powers of 23.

Original entry on oeis.org

23, 529, 12167, 6436343
Offset: 1

Views

Author

Artur Jasinski, Nov 09 2008

Keywords

Comments

In a variant of the ABC conjecture (see A120498) we look at triples (A,B,C) restricted to A+B=C, gcd(A,B)=1, and at the merit function L(A,B,C)=log(C)/log(rad(A*B*C)), where rad() is the squarefree kernel A007947, as usual. Watching for records in L() as C runs through the integers generates A147302. In this sequence here, we admit only the C of the form 23^x, see A009967, which avoids some early larger records that would be created by unrestricted C, and leads to a slower increase of the L-values.
For associated B for this case see A147641, for associated A see A147643.

Examples

			C= 23 is the first candidate (and therefore by definition a record). Scanning the pairs (A,B) for this C we have L-values of L(1,22,23) = 0.5035, L(2,21,23) = 0.456, ... L(6,17,23) = 0.404, L(7,16,23) = 0.542 ,... L(11,12,23) = 0.428. The largest L-value stems from (A=7,B=16) which means the representative triple of the first record is (A,B,C) = (7,16,23).
C= 23^2= 529 is the next candidate. Scanning again all (A,B) values subject to the constraints we achieve L(17,512,529) = 0.941... (Smaller ones like L(81,448,529) = 0.9123... are discarded). Since the L-value for C=529 is larger than the L-value for C=23, the next record is C=529 with representatives (A,B,C)= (17,512,529).
The third candidate is C= 23^3= 12167. This generates a maximum of L(162,12005,12167) = 1.1089... (smaller values like L(17,12150,12167) = 1.0039.. discarded) which is again larger than the maximum of the previous record (which was 0.941..) So the C-value of 12167 is again a record-holder.
		

Crossrefs

A159858 Numerator of Hermite(n, 1/23).

Original entry on oeis.org

1, 2, -1054, -6340, 3332716, 33496312, -17563075016, -247760738608, 129576612091280, 2356200115760672, -1229116100101646816, -27386829424951203392, 14249679514133063237824, 376202545407446604740480, -195237686946571258563550336, -5962787476468241626543090432
Offset: 0

Views

Author

N. J. A. Sloane, Nov 12 2009

Keywords

Comments

Consider any odd integer k. B(n) = k^n Hermite(n,1/k) satisfies the recurrence B(n) = 2*B(n-1) - 2*k^2*(n-1)*B(n-2) with B(0) = 1 and B(1) = 2. In particular, B(n) == 2*B(n-1) mod k, and B(n) is coprime to k. Therefore B(n) is the numerator of Hermite(n,1/k). - Robert Israel, Jun 27 2014

Examples

			Numerator of 1, 2/23, -1054/529, -6340/12167, 3332716/279841, 33496312/6436343, -17563075016/148035889, -247760738608/3404825447, 129576612091280/78310985281...
		

Crossrefs

Cf. A009967 (denominators).

Programs

  • Magma
    [Numerator((&+[(-1)^k*Factorial(n)*(2/23)^(n-2*k)/( Factorial(k) *Factorial(n-2*k)): k in [0..Floor(n/2)]])): n in [0..30]]; // G. C. Greubel, Jun 09 2018
  • Maple
    A159858 := proc(n)
            orthopoly[H](n,1/23) ;
            numer(%) ;
    end proc: # R. J. Mathar, Feb 16 2014
  • Mathematica
    Numerator[Table[HermiteH[n, 1/23], {n, 0, 30}]] (* Vladimir Joseph Stephan Orlovsky, Jun 22 2011 *)
  • PARI
    a(n)=numerator(polhermite(n,1/23)) \\ Charles R Greathouse IV, Jan 29 2016
    

Formula

D-finite with recurrence a(n) - 2*a(n-1) + 1058*(n-1)*a(n-2) = 0. [DLMF] - R. J. Mathar, Feb 16 2014
a(n) = 23^n * Hermite(n,1/23). This does satisfy the above formula. - Robert Israel, Jun 27 2014
From G. C. Greubel, Jun 09 2018: (Start)
E.g.f.: exp(2*x-529*x^2).
a(n) = numerator(Sum_{k=0..floor(n/2)} (-1)^k*n!*(2/23)^(n-2*k)/(k!*(n-2*k)!)). (End)

A009990 Powers of 46.

Original entry on oeis.org

1, 46, 2116, 97336, 4477456, 205962976, 9474296896, 435817657216, 20047612231936, 922190162669056, 42420747482776576, 1951354384207722496, 89762301673555234816, 4129065876983540801536, 189937030341242876870656, 8737103395697172336050176, 401906756202069927458308096
Offset: 0

Views

Author

Keywords

Comments

Same as Pisot sequences E(1, 46), L(1, 46), P(1, 46), T(1, 46). Essentially same as Pisot sequences E(46, 2116), L(46, 2116), P(46, 2116), T(46, 2116). See A008776 for definitions of Pisot sequences.
The compositions of n in which each natural number is colored by one of p different colors are called p-colored compositions of n. For n >= 1, a(n) equals the number of 46-colored compositions of n such that no adjacent parts have the same color. - Milan Janjic, Nov 17 2011

Crossrefs

Programs

Formula

G.f.: 1/(1-46*x). - Philippe Deléham, Nov 24 2008
a(n) = 46^n; a(n) = 46*a(n-1), a(0)=1. - Vincenzo Librandi, Nov 21 2010
From Elmo R. Oliveira, Jul 10 2025: (Start)
E.g.f.: exp(46*x).
a(n) = A000079(n)*A009967(n). (End)

A180732 23^a(n) is smallest power of 23 beginning with n.

Original entry on oeis.org

0, 1, 7, 10, 2, 5, 8, 33, 11, 36, 14, 3, 28, 6, 42, 31, 20, 9, 34, 23, 12, 106, 1, 37, 26, 15, 4, 51, 40, 29, 123, 18, 347, 7, 43, 137, 32, 220, 21, 256, 10, 245, 46, 234, 35, 129, 505, 24, 400, 13, 248, 2, 49, 378, 38, 179, 461, 27, 215, 497, 16, 204, 486, 5, 193, 475, 41, 135
Offset: 1

Views

Author

Daniel Mondot, Sep 18 2010

Keywords

Crossrefs

A382535 Consecutive states of Lehmer's original linear congruential pseudo-random number generator 23*s mod (10^8+1) when started at s=1.

Original entry on oeis.org

1, 23, 529, 12167, 279841, 6436343, 48035888, 4825413, 10984498, 52643452, 10799384, 48385830, 12874079, 96103815, 10387723, 38917627, 95105413, 87424478, 10762974, 47548400, 93613190, 53103349, 21377015, 91671341, 8440822, 94138905, 65194794, 99480248
Offset: 1

Views

Author

Sean A. Irvine, May 25 2025

Keywords

Comments

Periodic with period 5882352.
This is the first linear congruential pseudo-random number generator described in the literature. As such, it is the forerunner of one of the most widely used techniques for generating pseudo-random numbers.

Crossrefs

Cf. A009967.
Cf. A096550-A096561 (other pseudo-random number generators).

Programs

  • Mathematica
    NestList[Mod[23*#, 10^8 + 1] &, 1, 50] (* Paolo Xausa, May 26 2025 *)

Formula

a(n) = 23 * a(n-1) mod (10^8+1).
Showing 1-10 of 38 results. Next