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 14 results. Next

A107689 Primes with digital product = 3.

Original entry on oeis.org

3, 13, 31, 113, 131, 311, 11113, 11131, 11311, 113111, 131111, 311111, 11111131, 11111311, 11113111, 11131111, 111111113, 111111131, 111113111, 131111111, 11111111113, 11111111131, 11113111111, 11131111111, 31111111111
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Mathematica
    Flatten[ Table[ Select[ Sort[ FromDigits /@ Permutations[ Flatten[{3, Table[1, {n}]}]]], PrimeQ[ # ] &], {n, 0, 12}]]
  • Python
    from sympy import isprime
    def agen():
      digits = 0
      while True:
        for i in range(digits+1):
          t = int("1"*(digits-i) + "3" + "1"*i)
          if isprime(t): yield t
        digits += 1
    g = agen()
    print([next(g) for i in range(25)]) # Michael S. Branicky, Mar 13 2021

A107612 Primes with digital product = 2.

Original entry on oeis.org

2, 211, 2111, 111121, 111211, 112111, 1111211, 1111111121, 1111211111, 1121111111, 111111211111, 111211111111, 2111111111111, 111111111111112111, 111111112111111111, 111111211111111111, 112111111111111111
Offset: 1

Views

Author

Zak Seidov, May 17 2005

Keywords

Comments

Corresponding indices of primes in A107611. Cf. A053666, A101987.

Crossrefs

Programs

  • Maple
    for i from 0 to 30 do it:=sum(10^j, j=0..i): for k from 0 to i do if isprime(it+10^k) then printf(`%d,`, it+10^k) fi: od:od: (Sellers)
  • Mathematica
    Flatten[ Table[ Select[ Sort[ FromDigits /@ Permutations[ Flatten[{2, Table[1, {n}]}]]], PrimeQ[ # ] &], {n, 0, 19}]] (* Robert G. Wilson v, May 19 2005 *)
    Select[Flatten[Table[FromDigits/@Permutations[PadRight[{2},n,1]],{n,20}]],PrimeQ]//Sort (* Harvey P. Dale, May 28 2017 *)

Formula

A107612(n) = prime(A107611(n)).

Extensions

More terms from Robert G. Wilson v and James Sellers, May 19 2005

A107698 Smallest prime whose digital product = n or 0 if impossible.

Original entry on oeis.org

11, 2, 3, 41, 5, 23, 7, 181, 19, 251, 0, 43, 0, 127, 53, 281, 0, 29, 0, 541, 37, 0, 0, 83, 11551, 0, 139, 47, 0, 523, 0, 1481, 0, 0, 157, 149, 0, 0, 0, 12451, 0, 67, 0, 0, 59, 0, 0, 283, 11177, 2551, 0, 0, 0, 239, 0, 1187, 0, 0, 0, 1453, 0, 0, 79, 881, 0, 0, 0, 0, 0, 257, 0
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Comments

Zeros appear at A068191.

Examples

			a(20)=541 because 5*4*1=20 and there is no prime less than a(20) which exhibits this characteristic.
		

Crossrefs

Programs

  • Mathematica
    f[n_] := If[ Max[ First /@ FactorInteger[n]] > 7, 0, p = 1; While[Times @@ IntegerDigits[ Prime[p]] != n, p++ ]; Prime[p]]; Table[ f[n], {n, 30}]

A107690 Primes with digital product = 4.

Original entry on oeis.org

41, 4111, 11411, 12211, 21121, 21211, 22111, 112121, 1114111, 11111141, 11141111, 111112121, 111121121, 112111211, 112112111, 121111121, 121112111, 122111111, 212111111, 1111111411, 1111411111, 11111121121, 11111121211, 11111211121
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(10^8) | &*Intseq(p) eq 4]; // Vincenzo Librandi, Jun 30 2017
  • Mathematica
    Flatten[ Table[ Select[ Sort[ FromDigits /@ Join[ Permutations[ Flatten[{4, Table[1, {n}]}]], Permutations[ Flatten[{2, 2, Table[1, {n - 1}]}] ]]], PrimeQ[ # ] &], {n, 0, 10}]]

A107691 Primes with digital product = 5.

Original entry on oeis.org

5, 151, 1151, 1511, 511111, 1111151, 115111111, 1111115111, 1115111111, 1151111111, 111111111511, 111511111111, 1111151111111, 5111111111111, 111111151111111, 111151111111111, 5111111111111111, 111115111111111111111, 1111111111111111111511
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(3*10^8) | &*Intseq(p) eq 5]; // Vincenzo Librandi, Jul 27 2016
  • Maple
    select(isprime,[seq(seq((10^m-1)/9 + 4*10^j,j=0..m-1),m=1..40)]); # Robert Israel, Jan 03 2017
  • Mathematica
    Flatten[ Table[ Select[ Sort[ FromDigits /@ Permutations[Flatten[{5, Table[1, {n}]} ]]], PrimeQ[ # ] &], {n, 0, 21}]]
    Select[Prime[Range[3 10^6]], Times@@IntegerDigits[#] == 5 &] (* Vincenzo Librandi, Jul 27 2016 *)

A107692 Primes whose product of digits is 6.

Original entry on oeis.org

23, 61, 1123, 1213, 1231, 1321, 2113, 2131, 2311, 3121, 11161, 11213, 11321, 12113, 13121, 16111, 31121, 111611, 611111, 1111213, 1112113, 1112131, 1131121, 1211311, 2111311, 3112111, 11111161, 11112113, 11211131, 11231111, 11312111
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Mathematica
    Union[ Flatten[ Table[ Select[ Sort[ FromDigits /@ Join[ Permutations[ Flatten[{6, Table[1, {n}]}]], Permutations[ Flatten[{2, 3, Table[ 1, {n - 1}]}] ]]], PrimeQ[ # ] &], {n, 0, 7}]]]
    Select[Prime[Range[750000]],Times@@IntegerDigits[#]==6&] (* Harvey P. Dale, May 29 2016 *)
  • Python
    from sympy import prod, isprime
    from sympy.utilities.iterables import multiset_permutations
    def agen(maxdigits):
        for digs in range(1, maxdigits+1):
            for mp in multiset_permutations("1"*(digs-1) + "236", digs):
                if prod(map(int, mp)) == 6:
                    t = int("".join(mp))
                    if isprime(t): yield t
    print(list(agen(8))) # Michael S. Branicky, Jun 16 2021

A107695 Primes with digital product = 9.

Original entry on oeis.org

19, 191, 313, 331, 911, 11119, 111119, 111191, 113131, 131113, 131311, 911111, 1131113, 1131131, 1311131, 1311311, 3111131, 3113111, 11111119, 11111911, 11911111, 111111313, 111111331, 111113113, 111113131, 111131131, 111133111
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(3*10^7) | &*Intseq(p) eq 9]; // Vincenzo Librandi, Jul 27 2016
  • Mathematica
    Union[ Flatten[ Table[ Select[ Sort[ FromDigits /@ Join[ Permutations[ Flatten[{9, Table[1, {n}]}]], Permutations[ Flatten[{3, 3, Table[1, {n - 1}]}]]]], PrimeQ[ # ] & ], {n, 0, 8}]]]
    Select[Prime[Range[3 10^6]], Times@@IntegerDigits[#] == 9 &] (* Vincenzo Librandi, Jul 27 2016 *)

A107696 Primes with digital product = 10.

Original entry on oeis.org

251, 521, 11251, 12511, 15121, 25111, 111521, 115211, 121151, 151121, 152111, 211151, 511211, 11152111, 11511211, 12111511, 15111211, 15121111, 51111211, 111121151, 111512111, 112111511, 112151111, 112511111, 115211111, 121511111, 151211111
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(3*10^6) | &*Intseq(p) eq 10]; // Vincenzo Librandi, Jul 27 2016
  • Mathematica
    Flatten[ Table[ Select[ Sort[ FromDigits /@ Permutations[ Flatten[{2, 5, Table[1, {n}]} ]]], PrimeQ[ # ] &], {n, 0, 8}]]
    Select[Prime[Range[3 10^6]], Times@@IntegerDigits[#] == 10 &] (* Vincenzo Librandi, Jul 27 2016 *)

A107694 Primes with digital product = 8.

Original entry on oeis.org

181, 241, 421, 811, 1181, 1811, 2141, 2221, 2411, 4211, 8111, 21221, 141121, 142111, 411211, 1111181, 1112141, 1121221, 1211141, 1211411, 1212121, 2111411, 2121121, 2211211, 2221111, 2411111, 4121111, 4211111, 11221211, 12111221, 12121121
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(3*10^7) | &*Intseq(p) eq 8]; // Vincenzo Librandi, Jul 27 2016
  • Mathematica
    Union[ Flatten[ Table[ Select[ Sort[ FromDigits /@ Join[ Permutations[ Flatten[{8, Table[1, {n}]}]], Permutations[ Flatten[{2, 4, Table[1, {n - 1}]}]], Permutations[ Flatten[{2, 2, 2, Table[1, {n - 2}]}] ]]], PrimeQ[ # ] & ], {n, 0, 7}]]]
    Select[Prime[Range[3 10^6]], Times@@IntegerDigits[#] == 8 &] (* Vincenzo Librandi, Jul 27 2016 *)

A107697 Primes with digital product = 12.

Original entry on oeis.org

43, 223, 431, 1223, 1621, 2161, 2213, 3221, 6121, 6211, 11261, 11621, 12161, 12611, 13411, 21611, 26111, 41113, 41131, 61121, 61211, 111143, 111341, 111431, 112213, 114113, 114311, 121123, 121321, 122131, 123121, 131221, 141131, 141311, 143111
Offset: 1

Views

Author

Zak Seidov and Robert G. Wilson v, May 20 2005

Keywords

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(1000000) | &*Intseq(p) eq 12]; // Vincenzo Librandi, Jul 27 2016
  • Mathematica
    Union[ Flatten[ Table[ Select[ Sort[ FromDigits /@ Join[ Permutations[ Flatten[{2, 6, Table[1, {n - 1}]}]], Permutations[ Flatten[{3, 4, Table[1, {n - 1}]}]], Permutations[ Flatten[{2, 2, 3, Table[1, {n - 2}]}] ]]], PrimeQ[ # ] & ], {n, 0, 5}]]]
    Select[Prime[Range[75000]], Times@@IntegerDigits[#] == 12 &] (* Vincenzo Librandi, Jul 27 2016 *)
Showing 1-10 of 14 results. Next