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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A123299 Prime sums of 13 positive 5th powers.

Original entry on oeis.org

13, 137, 199, 317, 379, 503, 683, 739, 863, 1049, 1129, 1223, 1229, 1409, 1433, 1471, 1613, 1619, 1831, 1949, 1979, 2011, 2221, 2339, 2543, 2549, 2729, 2791, 2909, 2917, 2971, 3089, 3137, 3299, 3307, 3323, 3331, 3361, 3511, 3541, 3659, 3863, 3877, 3931, 4049
Offset: 1

Views

Author

Jonathan Vos Post, Sep 24 2006

Keywords

Examples

			a(1) = 13 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5.
a(2) = 137 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 2^5 + 2^5 + 2^5 + 2^5.
a(3) = 199 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5.
a(4) = 317 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 2^5 + 2^5 + 3^5.
		

Crossrefs

Programs

  • Mathematica
    up = 4100; q = Range[up^(1/5)]^5; a = {0}; Do[b = Select[ Union@ Flatten@ Table[e + a, {e, q}], # <= up &]; a = b, {k, 13}]; Select[a, PrimeQ] (* Giovanni Resta, Jun 12 2016 *)

Formula

A000040 INTERSECTION A123299.

Extensions

a(10)-a(45) from Giovanni Resta, Jun 12 2016

A336536 Numbers n that can be written as both the sum of two nonzero fourth powers and the sum of three nonzero fourth powers.

Original entry on oeis.org

4802, 57122, 76832, 260642, 388962, 617057, 913952, 1229312, 1847042, 1957682, 3001250, 3502322, 3748322, 3959297, 4170272, 4626882, 6223392, 6837602, 6959682, 9872912, 11529602, 14623232, 19668992, 21112002, 27691682, 29552672, 31322912, 31505922, 35701250, 40127377, 40302242, 46712801, 48020000, 48355137
Offset: 1

Views

Author

Robert Israel, Jul 24 2020

Keywords

Comments

The fourth powers are not necessarily distinct.
If n is in the sequence, then so is k^4*n for every k.
The sum of two nonzero fourth powers is never a fourth power (a case of Fermat's last theorem).

Examples

			a(3) = 76832 is in the sequence because 76832 = 14^4 + 14^4 = 6^4 + 10^4 + 16^4.
a(6) = 617057 is in the sequence because 617057 = 7^4 + 28^4 = 3^4 + 20^4 + 26^4.
		

Crossrefs

Intersection of A003336 and A003337.

Programs

  • Maple
    N:= 10^8: # for terms <= N
    F1:= {seq(i^4,i=1..floor(N^(1/4)))}: n1:= nops(F1):
    F2:= select(`<=`,{seq(seq(F1[i]+F1[j],i=1..j),j=1..nops(F1))},N):
    F3:= select(`<=`,{seq(seq(s+t,s=F1),t=F2)},N):
    sort(convert(F3 intersect F2,list));
  • Python
    def aupto(lim):
      p1 = set(i**4 for i in range(1, int(lim**.25)+2) if i**4 <= lim)
      p2 = set(a+b for a in p1 for b in p1 if a+b <= lim)
      p3 = set(apb+c for apb in p2 for c in p1 if apb+c <= lim)
      return sorted(p3 & p2)
    print(aupto(5*10**7)) # Michael S. Branicky, Mar 18 2021

A020896 Positive numbers k such that k = x^5 + y^5 has a solution in nonzero integers x, y.

Original entry on oeis.org

2, 31, 33, 64, 211, 242, 244, 275, 486, 781, 992, 1023, 1025, 1056, 1267, 2048, 2101, 2882, 3093, 3124, 3126, 3157, 3368, 4149, 4651, 6250, 6752, 7533, 7744, 7775, 7777, 7808, 8019, 8800, 9031, 10901, 13682, 15552, 15783, 15961, 16564
Offset: 0

Views

Author

Keywords

Comments

68101 = (15/2)^5 + (17/2)^5 is believed to be the smallest positive integer k which is the sum of two nonzero fifth powers of rational numbers but not the sum of two nonzero fifth powers of integers.

Examples

			31 = 2^5 + (-1)^5.
		

References

  • J.-P. Allouche and J. Shallit, Automatic Sequences, Cambridge Univ. Press, 2003, p. 99.

Crossrefs

Programs

  • Mathematica
    Select[Union[Total/@(Select[Tuples[Range[-8,8],{2}], !MemberQ[#, 0]&]^5)],#>0&]  (* Harvey P. Dale, Apr 03 2011 *)

Formula

See Theorem 3.5.6 of J.-P. Allouche and J. Shallit, Automatic Sequences, Cambridge Univ. Press, 2003, p. 99.

A123300 Prime sums of 14 positive 5th powers.

Original entry on oeis.org

107, 293, 349, 653, 659, 839, 1013, 1019, 1223, 1279, 1409, 1559, 1583, 1621, 1801, 1831, 1949, 2011, 2129, 2153, 2309, 2333, 2339, 2347, 2371, 2551, 2699, 2707, 2731, 2879, 2917, 3083, 3121, 3169, 3191, 3301, 3331, 3449, 3457, 3511, 3541, 3659, 3691, 3761, 3847, 4019, 4027, 4051
Offset: 1

Views

Author

Jonathan Vos Post, Sep 25 2006

Keywords

Examples

			a(1) = 107 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 2^5 + 2^5 + 2^5.
a(2) = 293 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5.
a(3) = 349 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 2^5 + 2^5 + 2^5 + 3^5.
a(4) = 653 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 1^5 + 2^5 + 2^5 + 2^5 + 2^5 + 2^5 + 3^5 + 3^5.
		

Crossrefs

Programs

  • Mathematica
    up = 5000; q = Range[up^(1/5)]^5; a={0}; Do[b = Select[Union@ Flatten@ Table[e + a, {e, q}], # <= up &]; a = b, {k, 14}]; Select[a, PrimeQ] (* Giovanni Resta, Jun 12 2016 *)

Formula

A000040 INTERSECTION A123295.

Extensions

More terms from Harvey P. Dale, Jan 01 2015
4 missing terms from Giovanni Resta, Jun 12 2016

A182198 Primes of form a^2 + b^2 such that a^4 + b^4 is prime.

Original entry on oeis.org

2, 5, 13, 17, 29, 37, 41, 53, 73, 89, 137, 149, 157, 181, 257, 269, 281, 293, 313, 349, 373, 397, 401, 409, 421, 461, 541, 557, 577, 593, 661, 709, 733, 757, 769, 773, 797, 853, 937, 953, 1021, 1049, 1069, 1181, 1237, 1277, 1301, 1373, 1429, 1433, 1453, 1489
Offset: 1

Views

Author

Thomas Ordowski, Apr 20 2012

Keywords

Examples

			13 = 2^2 + 3^2, 2^4 + 3^4 = 97 is prime.
		

Crossrefs

Subsequence of A002313.
Cf. A003336 (numbers that are the sum of 2 nonzero 4th powers).
Cf. A002645 (quartan primes: primes of the form x^4 + y^4).

Programs

  • Mathematica
    nn = 40; t = {}; Do[c = a^2 + b^2; If[c < nn^2 && PrimeQ[c] && PrimeQ[a^4 + b^4], AppendTo[t, c]], {a, nn}, {b, a}]; Sort[t] (* T. D. Noe, Apr 22 2012 *)
    Take[#[[1]]^2+#[[2]]^2&/@Select[Tuples[Range[40],2],AllTrue[{#[[1]]^2+ #[[2]]^2, #[[1]]^4+#[[2]]^4},PrimeQ]&]//Union,60] (* Harvey P. Dale, Jun 25 2018 *)
  • PARI
    list(lim)=my(v=List(),t);lim\=1;for(x=1,sqrtint(lim),for(y=1, min(sqrtint(lim-x^2),x), if(isprime(t=x^2+y^2)&&isprime(x^4+y^4), listput(v,t)))); vecsort(Vec(v),,8) \\ Charles R Greathouse IV, Apr 22 2012

A343913 Positive integers m such that 2*m^2 - 1 = x^4 + y^4 for some nonnegative integers x and y with |x - y| > 1.

Original entry on oeis.org

71, 347, 1193, 2139, 2709, 17823, 18337, 26057, 32847, 34037, 65793, 87519, 159541, 245573, 383037, 421957, 489731, 520547, 574841, 800589, 1291333, 2010341, 2113003, 2990187, 4528667, 7430553, 8284063, 8402417, 8520567, 9220519, 9865989, 10621507, 11961043, 12335203, 16405581, 17648561, 22224647, 22918853, 24171273
Offset: 1

Views

Author

Zhi-Wei Sun, May 03 2021

Keywords

Comments

Conjecture: The sequence has infinitely many terms.
Clearly all the terms must be odd and not divisible by 5. Note also that 2*(n^2+n+1)^2 - 1 = n^4 + (n+1)^4.
See also A343917 for a similar conjecture.

Examples

			a(1) = 71, and 2*71^2 - 1 = 10^4 + 3^4 with |10 - 3| > 1.
a(53) = 99532937, and 2*99532937^2 - 1 = 19813611095691937 = 11337^4 + 7576^4 with |11337 - 7576| > 1.
		

Crossrefs

Programs

  • Maple
    N:= 10^18: # for all terms <= sqrt(N)
    R:= {}: count:= 0:
    for x from 1 while 2*x^4 < 2*N-1 do
      for y from x+3 by 2 do
        v:= (x^4 + y^4 + 1)/2;
        if v > N then break fi;
        if issqr(v) then
          m:= sqrt(v);
          if not member(m,R) then
             count:= count+1; R:= R union {m};
          fi fi
    od od:
    sort(convert(R,list)); # Robert Israel, May 04 2021
  • Mathematica
    QQ[n_]:=IntegerQ[n^(1/4)];
    n=0;Do[Do[If[QQ[2*m^2-1-(2x)^4]&&Abs[2x-(2*m^2-1-(2x)^4)^(1/4)]>1,n=n+1;Print[n," ",m];Goto[aa]],{x,0,((2m^2-1)^(1/4))/2}];Label[aa],{m,1,25000000}]

A343917 Positive integers m with 2*m^2 - 2^4 = x^4 + y^4 for some nonnegative integers x and y with |x-y| > 2.

Original entry on oeis.org

284, 1388, 2139, 4772, 8556, 8971, 10836, 21163, 28847, 45707, 54507, 71292, 73348, 95127, 101503, 104228, 131388, 136148, 263172, 350076, 638164, 982292, 1532148, 1687828, 1705407, 1958924, 2082188, 2299364, 2360347, 2728379, 3202356, 4042799, 5046771, 5165332, 5235323, 5560627, 7191079, 7740547, 8041364
Offset: 1

Views

Author

Zhi-Wei Sun, May 04 2021

Keywords

Comments

Conjecture: The sequence has infinitely many terms.
It is easy to see that no term is divisible by 5. In the b-file we list all the 62 terms not exceeding 10^8.
Note that 2*(n^2+3)^2 - 2^4 = (n+1)^4 + (n-1)^4 with (n+1) - (n-1) = 2. This implies that any integer n > 4 can be written as x + y + 2^(z-1) with x,y,z positive integers such that x^4 + y^4 + (2^z)^4 is twice a square.
See also A343913 for a similar conjecture.

Examples

			a(1) = 284, and 2*284^2 - 2^4 = 20^4 + 6^4 with |20-6| > 2.
a(62) = 97077407, and 2*97077407^2 - 2^4 = 18848045899687282 = 11563^4 + 5583^4 with |11563-5583| > 2.
		

Crossrefs

Programs

  • Mathematica
    QQ[n_]:=IntegerQ[n^(1/4)];
    n=0;Do[Do[If[QQ[2*m^2-16-x^4]&&(2*m^2-16-x^4)^(1/4)-x>2,n=n+1;Print[n," ",m];Goto[aa]],{x,0,(m^2-8)^(1/4)}];Label[aa],{m,3,8041364}]

A047715 Numbers that are the sum of 4 but no fewer nonzero fourth powers.

Original entry on oeis.org

4, 19, 34, 49, 64, 84, 99, 114, 129, 164, 179, 194, 244, 259, 274, 289, 304, 324, 339, 354, 369, 419, 434, 499, 514, 529, 544, 594, 609, 628, 643, 658, 673, 674, 708, 723, 738, 769, 784, 788, 803, 849, 868, 883, 898, 913, 963, 978, 1024, 1043, 1138, 1153
Offset: 1

Views

Author

Arlin Anderson (starship1(AT)gmail.com)

Keywords

Comments

First differs from A003338 at term 64: A003338(64) = 1393 is also a term of A003337, so not a term here. - Michael S. Branicky, Apr 19 2021

Crossrefs

Cf. A000583, A002377, A003338 (sum of 4), A003337 (sum of 3), A003336 (sum of 2), A344188, A344187.

Programs

  • Python
    limit = 1153
    from functools import lru_cache
    qd = [k**4 for k in range(1, int(limit**.25)+2) if k**4 + 3 <= limit]
    qds = set(qd)
    @lru_cache(maxsize=None)
    def findsums(n, m):
      if m == 1: return {(n,)} if n in qds else set()
      return set(tuple(sorted(t+(q,))) for q in qds for t in findsums(n-q, m-1))
    A003338s = set(n for n in range(4, limit+1) if len(findsums(n, 4)) >= 1)
    A003337s = set(n for n in range(3, limit+1) if len(findsums(n, 3)) >= 1)
    A003336s = set(n for n in range(2, limit+1) if len(findsums(n, 2)) >= 1)
    print(sorted(A003338s - A003337s - A003336s - qds)) # Michael S. Branicky, Apr 19 2021

Formula

Equals A003338 - A344188 - A344187 - A000583, where "-" denotes "set difference". - Sean A. Irvine, May 15 2021

A123033 Prime sums of 4 positive 5th powers.

Original entry on oeis.org

97, 277, 761, 1511, 1753, 2081, 3221, 3643, 6197, 7517, 7841, 8263, 10067, 10399, 10903, 16903, 25639, 32771, 32833, 33013, 33647, 33889, 35059, 36137, 39019, 40577, 40819, 48563, 49639, 57383, 59083, 59567, 60317, 61129, 62207, 63199, 66383, 66889, 100003
Offset: 1

Views

Author

Jonathan Vos Post, Sep 24 2006

Keywords

Comments

Primes in the sumset {A000584 + A000584 + A000584 + A000584}.
There must be an odd number of odd terms in the sum, either one even and 3 odd terms (as with 1^5 + 1^5 + 2^5 + 3^5 and 761 = 2^5 + 3^5 + 3^5 + 3^5) or three even terms and one odd term (as with 97 = 1^5 + 2^5 + 2^5 + 2^5 and 3221 = 2^5 + 2^5 + 2^5 + 5^5). The sum of two positive 5th powers (A003347), other than 2 = 1^5 + 1^5, cannot be prime.

Examples

			a(1) = 97 = 1^5 + 2^5 + 2^5 + 2^5.
a(2) = 277 = 1^5 + 1^5 + 2^5 + 3^5.
a(3) = 761 = 2^5 + 3^5 + 3^5 + 3^5.
a(7) = 3221 = 2^5 + 2^5 + 2^5 + 5^5.
		

Crossrefs

Programs

  • Mathematica
    up = 10^6; q = Range[up^(1/5)]^5; a = {0}; Do[b = Select[ Union@ Flatten@Table[e + a, {e, q}], # <= up &]; a = b, {k, 4}]; Select[a, PrimeQ] (* Giovanni Resta, Jun 13 2016 *)

Formula

A000040 INTERSECTION A003349.

Extensions

More terms from Alois P. Heinz, Aug 12 2015

A123034 Prime sums of 5 positive 5th powers.

Original entry on oeis.org

5, 67, 1301, 1543, 2113, 2293, 2777, 3191, 3253, 3347, 3371, 3433, 3613, 4339, 5237, 5417, 5659, 6229, 6737, 7307, 7549, 7873, 8053, 8537, 8803, 9377, 9439, 9619, 9857, 10099, 11177, 11423, 11927, 12743, 15797, 15859, 16811, 17053, 17183, 18679, 18919, 19163
Offset: 1

Views

Author

Jonathan Vos Post, Sep 24 2006

Keywords

Comments

Primes in the sumset {A000584 + A000584 + A000584 + A000584 + A000584}.
There must be an odd number of odd terms in the sum, either 5 odd terms (as with 5 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5 and 16811 = 1^5 + 1^5 + 1^5 + 1^5 + 7^5), two even and 3 odd terms (as with 67 = 1^5 + 1^5 + 1^5 + 2^5 + 2^5 and 1301 = 1^5 + 1^5 + 2^5 + 3^5 + 4^5) or four even terms and one odd term (as with 3253 = 2^5 + 2^5 + 2^5 + 2^5 + 5^5). The sum of two positive 5th powers (A003347), other than 2 = 1^5 + 1^5, cannot be prime.

Examples

			a(1) = 5 = 1^5 + 1^5 + 1^5 + 1^5 + 1^5.
a(2) = 67 = 1^5 + 1^5 + 1^5 + 2^5 + 2^5.
a(3) = 1301 = 1^5 + 1^5 + 2^5 + 3^5 + 4^5.
a(4) = 1543 = 1^5 + 2^5 + 3^5 + 3^5 + 4^5.
a(5) = 2113 = 1^5 + 2^5 + 2^5 + 4^5 + 4^5.
a(6) = 3191 = 1^5 + 1^5 + 2^5 + 2^5 + 5^5.
a(7) = 4339 = 3^5 + 4^5 + 4^5 + 4^5 + 4^5.
		

Crossrefs

Programs

  • Mathematica
    Take[Select[Union[Total/@Tuples[Range[10]^5,5]],PrimeQ],60] (* Harvey P. Dale, Jul 21 2014 *)

Formula

A000040 INTERSECTION A003350.

Extensions

Corrected and extended by Harvey P. Dale, Jul 21 2014
Previous Showing 51-60 of 76 results. Next