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 1-5 of 5 results.

A019546 Primes whose digits are primes; primes having only {2, 3, 5, 7} as digits.

Original entry on oeis.org

2, 3, 5, 7, 23, 37, 53, 73, 223, 227, 233, 257, 277, 337, 353, 373, 523, 557, 577, 727, 733, 757, 773, 2237, 2273, 2333, 2357, 2377, 2557, 2753, 2777, 3253, 3257, 3323, 3373, 3527, 3533, 3557, 3727, 3733, 5227, 5233, 5237, 5273, 5323, 5333, 5527, 5557
Offset: 1

Views

Author

R. Muller

Keywords

Comments

Intersection of A046034 and A000040; A055642(a(n)) = A193238(a(n)). - Reinhard Zumkeller, Jul 19 2011
Ribenboim mentioned in 2000 the following number as largest known term: 72323252323272325252 * (10^3120 - 1) / (10^20 - 1) + 1. It has 3120 digits, and was discovered by Harvey Dubner in 1992. Larger terms are 22557252272*R(15600)/R(10) and 2255737522*R(15600) where R(n) denotes the n-th repunit (see A002275): Both have 15600 digits and were found in 2002, also by Dubner (see Weisstein link). David Broadhurst reports in 2003 an even longer number with 82000 digits: (10^40950+1) * (10^20055+1) * (10^10374 + 1) * (10^4955 + 1) * (10^2507 + 1) * (10^1261 + 1) * (3*R(1898) + 555531001*10^940 - R(958)) + 1, see link. - Reinhard Zumkeller, Jan 13 2012
The smallest and largest primes that use exactly once the four prime decimal digits are respectively a(27)= 2357 and a(54) = 7523. - Bernard Schott, Apr 27 2023

References

  • Paulo Ribenboim, Prime Number Records (Chap 3), in 'My Numbers, My Friends', Springer-Verlag 2000 NY, page 76.

Crossrefs

Cf. A020463 (subsequence).
A093162, A093164, A093165, A093168, A093169, A093672, A093674, A093675, A093938 and A093941 are subsequences. - XU Pingya, Apr 20 2017

Programs

  • Haskell
    a019546 n = a019546_list !! (n-1)
    a019546_list = filter (all (`elem` "2357") . show )
                          ([2,3,5] ++ (drop 2 a003631_list))
    -- Or, much more efficient:
    a019546_list = filter ((== 1) . a010051) $
                          [2,3,5,7] ++ h ["3","7"] where
       h xs = (map read xs') ++ h xs' where
         xs' = concat $ map (f xs) "2357"
         f xs d = map (d :) xs
    -- Reinhard Zumkeller, Jul 19 2011
    
  • Magma
    [p: p in PrimesUpTo(5600) | Set(Intseq(p)) subset [2,3,5,7]]; // Bruno Berselli, Jan 13 2012
    
  • Mathematica
    Select[Prime[Range[700]], Complement[IntegerDigits[#], {2, 3, 5, 7}] == {} &] (* Alonso del Arte, Aug 27 2012 *)
    Select[Prime[Range[700]], AllTrue[IntegerDigits[#], PrimeQ] &] (* Ivan N. Ianakiev, Jun 23 2018 *)
    Select[Flatten[Table[FromDigits/@Tuples[{2,3,5,7},n],{n,4}]],PrimeQ] (* Harvey P. Dale, Apr 05 2025 *)
  • PARI
    is_A019546(n)=isprime(n) & !setminus(Set(Vec(Str(n))),Vec("2357")) \\ M. F. Hasler, Jan 13 2012
    
  • PARI
    print1(2); for(d=1,4, forstep(i=1,4^d-1,[1,1,2], p=sum(j=0,d-1,10^j*[2,3,5,7][(i>>(2*j))%4+1]); if(isprime(p), print1(", "p)))) \\ Charles R Greathouse IV, Apr 29 2015
    
  • Python
    from itertools import product
    from sympy import isprime
    A019546_list = [2,3,5,7]+[p for p in (int(''.join(d)+e) for l in range(1,5) for d in product('2357',repeat=l) for e in '37') if isprime(p)] # Chai Wah Wu, Jun 04 2021

Extensions

More terms from Cino Hilliard, Aug 06 2006
Thanks to Charles R Greathouse IV and T. D. Noe for massive editing support.

A083185 Palindromic primes using only nonprime digits (0,1,4,6,8,9).

Original entry on oeis.org

11, 101, 181, 191, 919, 10601, 11411, 16061, 16661, 18181, 18481, 19891, 19991, 91019, 94049, 94649, 94849, 94949, 96469, 98689, 1008001, 1114111, 1160611, 1180811, 1186811, 1190911, 1196911, 1409041, 1411141, 1444441, 1461641
Offset: 1

Views

Author

Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Apr 26 2003

Keywords

Crossrefs

Palindromes in A034844.

Programs

  • Mathematica
    Select[ Prime[ Range[111500]], IntegerDigits[ # ] == Reverse[ IntegerDigits[ # ]] && Union[ Join[ IntegerDigits[ # ], {0, 1, 4, 6, 8, 9}]] == {0, 1, 4, 6, 8, 9} & ]
    Select[Prime[Range[120000]],PalindromeQ[#]&&NoneTrue[IntegerDigits[#], PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 08 2018 *)

Extensions

Edited and extended by Patrick De Geest, Jun 11 2003

A083183 Smallest palindromic prime using only prime digits (2,3,5,7) and having a sum of digits = prime(n), or 0 if no such number exists.

Original entry on oeis.org

2, 3, 5, 7, 353, 373, 33533, 757, 35753, 75557, 77377, 3773773, 325777523, 327757723, 357575753, 32577577523, 32777777723, 35775757753, 72777777727, 3557577757553, 3777727277773, 3775777775773, 7777573757777
Offset: 1

Views

Author

Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Apr 26 2003

Keywords

Comments

Conjecture: no entry is zero.

Crossrefs

Extensions

Corrected and extended by Patrick De Geest, Jun 12 2003

A343714 Palindromic primes of the form p//q//reverse(p), where p is a prime (not necessarily palindromic) and q, of course, is a palindromic prime.

Original entry on oeis.org

353, 373, 727, 757, 11311, 13331, 19391, 31013, 31513, 33533, 37273, 37573, 39293, 71317, 71917, 73237, 77977, 79397, 97379, 97579, 1035301, 1092901, 1093901, 1175711, 1178711, 1273721, 1317131, 1335331, 1338331, 1513151, 1572751, 1633361, 1737371, 1793971
Offset: 1

Views

Author

Jon E. Schoenfield, May 08 2021

Keywords

Comments

Note that reverse(p) need not be a prime; e.g., a(7)=19391 is the concatenation of 19, 3, and 91=7*13. If a requirement were added that reverse(p) also be a prime, the result would be sequence A343715.

Examples

			353 is a term because it is a palindromic prime (A002385) and is the concatenation of 3 (a prime), 5 (a palindromic prime), and 3 (the reverse of 3).
31513 is a term in two ways: as the concatenation 3//151//3 and as the concatenation 31//5//13.
7392937 is a term in three ways: 7//39293//7, 73//929//37, and 739//2//937.
		

Crossrefs

A343715 Palindromic primes of the form p//q//reverse(p), where p, q, and reverse(p) are primes.

Original entry on oeis.org

353, 373, 727, 757, 11311, 13331, 31013, 31513, 33533, 37273, 37573, 39293, 71317, 71917, 73237, 77977, 79397, 97379, 97579, 1175711, 1178711, 1317131, 1335331, 1338331, 1513151, 1572751, 1737371, 1793971, 1917191, 1993991, 1995991, 3103013, 3106013, 3127213
Offset: 1

Views

Author

Jon E. Schoenfield, May 08 2021

Keywords

Comments

If reverse(p) were allowed to be nonprime, the result would be sequence A343714, which includes such terms as 19391.

Examples

			353 is a term because it is a palindromic prime (A002385) and is the concatenation of 3 (a prime), 5 (a palindromic prime), and 3 (the reverse of 3, and also a prime).
31513 is a term in two ways: as the concatenation 3//151//3 and as the concatenation 31//5//13.
7392937 is a term in three ways: 7//39293//7, 73//929//37, and 739//2//937.
		

Crossrefs

Showing 1-5 of 5 results.