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.

Previous Showing 11-18 of 18 results.

A257774 Numbers n such that the products of the decimal digits of n^2 and n^3 coincide, n^2 and n^3 are zeroless.

Original entry on oeis.org

1, 5, 7, 6057, 292839, 1295314, 4897814, 4967471, 5097886, 6010324, 6919146, 7068165, 7189558, 9465077, 15347958, 22842108, 24463917, 26754863, 43378366, 48810128, 48885128, 50833026, 54588458, 54649688, 68093171, 69925865, 69980346, 73390374, 74357144
Offset: 1

Views

Author

Pieter Post, May 08 2015

Keywords

Comments

This sequence is more sporadic than A257760. It appears there is no sequence for zeroless numbers n and n^3 such that the products of the decimal digits coincide, except for the trivial 1.

Examples

			5 is in the sequence since 5^2 = 25 and 5^3 = 125 and we have 2*5 = 1*2*5 = 10 > 0.
6057 is in the sequence since 6057^2 = 36687249 and 6057^3 = 222214667193 and we have 3*6*6*8*7*2*4*9 = 2*2*2*2*1*4*6*6*7*1*9*3 = 435456 > 0.
		

Crossrefs

Programs

  • Mathematica
    pod[n_] := Times@@IntegerDigits@n; Select[Range[10^7], pod[#^3] == pod[#^2] > 0 &] (* Giovanni Resta, May 08 2015 *)

Extensions

Corrected and extended by Giovanni Resta, May 08 2015

A345391 a(n) is the least proper multiple of n with the same set of decimal digits as n.

Original entry on oeis.org

11, 22, 33, 44, 55, 66, 77, 88, 99, 100, 1111, 1212, 1131, 1414, 1155, 1616, 1717, 1188, 1919, 200, 2121, 2222, 322, 2424, 225, 2262, 2727, 2828, 2929, 300, 1333, 3232, 3333, 3434, 3535, 3636, 3737, 3838, 3393, 400, 4141, 4242, 344, 4444, 4455, 644, 4747
Offset: 1

Views

Author

Rémy Sigrist, Jun 17 2021

Keywords

Crossrefs

Programs

  • PARI
    a(n) = { my (d=Set(digits(n))); forstep (m=2*n, oo, n, if (Set(digits(m))==d, return (m))) }
    
  • Python
    def a(n):
        kn, ss = 2*n, set(str(n))
        while set(str(kn)) != ss: kn += n
        return kn
    print([a(n) for n in range(1, 49)]) # Michael S. Branicky, Jun 17 2021

Formula

a(n) <= A020338(n) for any n > 0.

A387070 Remove every digit that appears in n from the decimal representation of n^2. If no digits remain, set a(n) = 0.

Original entry on oeis.org

0, 0, 4, 9, 16, 2, 3, 49, 64, 81, 0, 2, 44, 69, 96, 22, 25, 289, 324, 36, 4, 44, 484, 59, 576, 6, 7, 9, 74, 841, 9, 96, 104, 1089, 1156, 122, 129, 169, 1444, 1521, 16, 68, 176, 189, 1936, 202, 211, 2209, 230, 201, 2, 260, 704, 2809, 2916, 302, 313, 3249, 3364, 3481, 3, 372, 3844, 99, 9, 422, 435
Offset: 0

Views

Author

Ali Sada, Aug 15 2025

Keywords

Examples

			a(25) = 6 since 25^2 = 625 and once we remove the 2 and 5, we are left with 6.
a(26) = 7 since 26^2 = 676 and once we remove the 6, we are left with 7.
		

Crossrefs

Programs

  • Mathematica
    a[n_] := FromDigits[Select[IntegerDigits[n^2], FreeQ[IntegerDigits[n], #] &]]; Array[a, 100, 0] (* Amiram Eldar, Aug 16 2025 *)
  • PARI
    a(n)={my(S=Set(digits(n))); fromdigits(select(x->!setsearch(S,x), digits(n^2)))} \\ Andrew Howroyd, Aug 15 2025
    
  • Python
    def A387070(k):
        s = set(str(k))
        t = "".join(d for d in str(k**2) if d not in s)
        return int(t) if t != "" else 0
    print([A387070(n) for n in range(67)]) # Michael S. Branicky, Aug 16 2025

Formula

a(n) = A258682(n) for n <= 19.
From David A. Corneth, Aug 16 2025: (Start)
a(A029793(k)) = 0.
a(A029783(k)) = A029783(k)^2. (End)

A029794 Squares n such that sqrt(n) and n have the same set of digits.

Original entry on oeis.org

0, 1, 100, 10000, 1000000, 22676644, 23348224, 100000000, 107661376, 110103049, 125552025, 153388225, 160022500, 219899241, 504002500, 552532036, 605406025, 696643236, 1169366416, 1311526225, 2267664400
Offset: 1

Views

Author

Keywords

Comments

Only perfect squares are considered. Otherwise, this sequence would have to include numbers like 1234567890, since sqrt(1234567890) = 35136.41828644462161665823116758077037159... - Alonso del Arte, Jan 12 2020

Crossrefs

Cf. A029793.

Programs

  • Mathematica
    Select[Range[0, 199999], Union[IntegerDigits[#]] == Union[IntegerDigits[#^2]] &]^2 (* Alonso del Arte, Jan 12 2020 *)
  • PARI
    lista(nn) = {for (n=0, nn, if (Set(digits(n^2)) == Set(digits(n)), print1(n^2, ", ")););} \\ Michel Marcus, Apr 29 2018

Formula

a(n) = A029793(n)^2. - Michel Marcus, Apr 29 2018

Extensions

Offset corrected by Michel Marcus, Apr 29 2018

A232712 Least positive k (not a power of 10) such that k and k^n have the same set of digits.

Original entry on oeis.org

2, 4762, 107624, 35641, 39568, 1380796, 12635940, 40837596, 102349857, 102567384, 106342987, 129046873, 107623945, 231940678, 239607415, 368709154, 1023456789, 164758903, 176384592, 1023456789, 1023456789, 1023456789, 1023456789, 1023456789, 1023456789
Offset: 1

Views

Author

Arkadiusz Wesolowski, Nov 28 2013

Keywords

Comments

a(17) and a(20)-a(40) = A050278(1) = 1023456789, the smallest pandigital number. [Lars Blomberg, Dec 10 2013]

Crossrefs

Programs

  • PARI
    for(n=1, 6, k=1; until(Set(Vec(Str(k)))==Set(Vec(Str(k^n)))&&!(sumdigits(k)==1), k++); print1(k, ", "));

Extensions

a(14)-a(25) from Lars Blomberg, Dec 10 2013

A257968 Zeroless numbers n such that the product of digits of n, the product of digits of n^2 and the product of digits of n^3 form a geometric progression.

Original entry on oeis.org

1, 2, 38296, 151373, 398293, 422558, 733381, 971973, 2797318, 3833215, 6988327, 7271256, 8174876, 8732657, 9872323, 9981181, 11617988, 11798921, 14791421, 15376465, 15487926, 15625186, 16549885, 18543639, 21316582, 21492828, 22346329, 22867986, 23373644
Offset: 1

Views

Author

Pieter Post, May 15 2015

Keywords

Comments

This sequence appears to be infinite.

Examples

			38296 is in the sequence because the pod equals 2592 (=3*8*2*9*6), pod(38296^2) is 622080, pod(38296^3) is 149299200. 2592*240 = 622080 => 622080*240 = 149299200.
		

Crossrefs

Cf. A052382 (zeroless numbers), A007954 (product of digits).

Programs

  • Mathematica
    pod[n_]:=Times@@IntegerDigits@n; Select[Range[10^8], pod[#^3] pod[#] == pod[#^2]^2 >0 &] (* Vincenzo Librandi, May 16 2015 *)
  • PARI
    pod(n) = my(d = digits(n)); prod(k=1, #d, d[k]);
    isok(n) = (pd = pod(n)) && (pdd = pod(n^2)) && (pdd/pd == pod(n^3)/pdd); \\ Michel Marcus, May 30 2015
  • Python
    def pod(n):
        kk = 1
        while n > 0:
            kk= kk*(n%10)
            n =int(n//10)
        return kk
    for i in range (1,10**7):
        if pod(i**3)*pod(i)==pod(i**2)**2 and pod(i**2)!=0:
            print (i, pod(i),pod(i**2),pod(i**3),pod(i**2)//pod(i))
    

Formula

pod(n^3)/pod(n^2)=pod(n^2)/pod(n), where pod(n) = A007954(n).

Extensions

a(17)-a(29) from Giovanni Resta, May 15 2015

A258231 Numbers n such that both n and n squared contain exactly the same digits, and n is not divisible by 10.

Original entry on oeis.org

1, 4762, 4832, 10376, 10493, 11205, 12385, 14829, 23506, 24605, 26394, 34196, 36215, 48302, 49827, 68474, 71205, 72576, 74528, 79286, 79603, 79836, 94583, 94867, 96123, 98376, 100469, 100496, 100498, 100499, 100946, 102245, 102953, 103265, 103479, 103756
Offset: 1

Views

Author

Harvey P. Dale, Apr 23 2016

Keywords

Comments

If n is in this sequence, then n*10^k also satisfies the first portion of the definition for all k >= 0.

Examples

			4832 is a term because 4832 squared = 23348224 which contains exactly the same digits as 4832.
		

Crossrefs

Programs

  • Mathematica
    Select[Select[Range[200000],ContainsExactly[IntegerDigits[ #], IntegerDigits[ #^2]]&], !Divisible[#,10]&]
  • Python
    A258231_list = [n for n in range(10**6) if n % 10 and set(str(n)) == set(str(n**2))] # Chai Wah Wu, Apr 23 2016

A383328 Numbers that have the same set of digits as the sum of the squares of their digits.

Original entry on oeis.org

0, 1, 155, 224, 242, 334, 343, 422, 433, 505, 515, 550, 551, 1388, 1788, 1838, 1878, 1883, 1887, 3188, 3334, 3336, 3343, 3363, 3433, 3633, 3818, 3881, 4333, 5005, 5050, 5500, 6333, 7188, 7818, 7881, 8138, 8178, 8183, 8187, 8318, 8381, 8718, 8781, 8813, 8817, 8831
Offset: 1

Views

Author

Jean-Marc Rebert, Apr 23 2025

Keywords

Examples

			155 and 1^2 + 5^2 + 5^2 = 51 have the same set of digits {1,5}, so 155 is a term.
		

Crossrefs

Programs

  • Mathematica
    q[k_] := Module[{d = IntegerDigits[k]}, Union[d] == Union[IntegerDigits[Total[d^2]]]]; Select[Range[0, 10000], q] (* Amiram Eldar, Apr 23 2025 *)
  • PARI
    isok(k) = my(d=digits(k)); Set(d) == Set(digits(sum(i=1, #d, d[i]^2))); \\ Michel Marcus, May 13 2025
  • Python
    def ok(n): return set(s:=str(n)) == set(str(sum(int(d)**2 for d in s)))
    print([k for k in range(10**4) if ok(k)]) # Michael S. Branicky, Apr 23 2025
    
Previous Showing 11-18 of 18 results.