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 1-6 of 6 results.

A108388 Transmutable primes: Primes with distinct digits d_i, i=1,m (2<=m<=4) such that simultaneously exchanging all occurrences of any one pair (d_i,d_j), i<>j results in a prime.

Original entry on oeis.org

13, 17, 31, 37, 71, 73, 79, 97, 113, 131, 179, 191, 199, 313, 331, 337, 773, 911, 919, 1171, 1933, 3391, 7717, 9311, 11113, 11119, 11177, 11717, 11933, 33199, 33331, 77171, 77711, 77713, 79999, 97777, 99991, 113111, 131111, 131113, 131171, 131311
Offset: 1

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Author

Rick L. Shepherd, Jun 02 2005

Keywords

Comments

a(n) is a term iff a(n) is prime and binomial(m,2) 'transmutations' (see example) of a(n) are different primes. A083983 is the subsequence for m=2: one transmutation (The author of A083983, Amarnath Murthy, calls the result of such a digit-exchange a self-complement. {Because I didn't know until afterwards that this sequence was a generalization of A083983 and as this generalization always leaves some digits unchanged for m>2, I've chosen different terminology.}). A108389 ({1,3,7,9}) is the subsequence for m=4: six transmutations. Each a(n) corresponding to m=3 (depending upon its set of distinct digits) and having three transmutations is also a member of A108382 ({1,3,7}), A108383 ({1,3,9}), A108384 ({1,7,9}), or A108385 ({3,7,9}). The condition m>=2 only eliminates the repunit (A004022) and single-digit primes. The condition m<=4 is not a restriction because if there were more distinct digits, they would include even digits or the digit 5, in either case transmuting into a composite number. Some terms such as 1933 are reversible primes ("Emirps": A006567) and the reverse is also transmutable. The transmutable prime 3391933 has three distinct digits and is also a palindromic prime (A002385). The smallest transmutable prime having four distinct digits is A108389(0) = 133999337137 (12 digits).

Examples

			179 is a term because it is prime and its three transmutations are all prime:
exchanging ('transmuting') 1 and 7: 179 ==> 719 (prime),
exchanging 1 and 9: 179 ==> 971 (prime) and
exchanging 7 and 9: 179 ==> 197 (prime).
(As 791 and 917 are not prime, 179 is not a term of A068652 or A003459 also.).
Similarly, 1317713 is transmutable:
exchanging all 1's and 3s: 1317713 ==> 3137731 (prime),
exchanging all 1's and 7s: 1317713 ==> 7371173 (prime) and
exchanging all 3s and 7s: 1317713 ==> 1713317 (prime).
		

Crossrefs

Cf. A108382, A108383, A108384, A108385, A108386, A108389 (transmutable primes with four distinct digits), A083983 (transmutable primes with two distinct digits), A108387 (doubly-transmutable primes), A006567 (reversible primes), A002385 (palindromic primes), A068652 (every cyclic permutation is prime), A003459 (absolute primes).

Programs

  • Python
    from gmpy2 import is_prime
    from itertools import combinations, count, islice, product
    def agen(): # generator of terms
        for d in count(2):
            for p in product("1379", repeat=d):
                p, s = "".join(p), sorted(set(p))
                if len(s) == 1: continue
                if is_prime(t:=int(p)):
                    if all(is_prime(int(p.translate({ord(c):ord(d), ord(d):ord(c)}))) for c, d in combinations(s, 2)):
                        yield t
    print(list(islice(agen(), 50))) # Michael S. Branicky, Dec 15 2023

A108389 Transmutable primes with four distinct digits.

Original entry on oeis.org

133999337137, 139779933779, 173139331177, 173399913979, 177793993177, 179993739971, 391331737931, 771319973999, 917377131371, 933971311913, 997331911711, 1191777377177, 9311933973733, 9979333919939, 19979113377173, 31997131171111, 37137197179931, 37337319113911
Offset: 1

Views

Author

Rick L. Shepherd, Jun 02 2005

Keywords

Comments

This sequence is a subsequence of A108386 and of A108388. See the latter for the definition of transmutable primes and many more comments. Are any terms here doubly-transmutable also; i.e., terms of A108387? Palindromic too? Terms also of some other sequences cross-referenced below? a(7)=771319973999 is also a reversible prime (emirp). a(12)=9311933973733 also has the property that simultaneously removing all its 1's (93933973733), all its 3s (9119977) and all its 9s (3113373733) result in primes (but removing all 7s gives 93119339333=43*47*59*83*97^2, so a(12) is not also a term of A057876). Any additional terms have 14 or more digits.

Examples

			a(0)=133999337137 is the smallest transmutable prime with four distinct digits (1,3,7,9):
exchanging all 1's and 3's: 133999337137 ==> 311999117317 (prime),
exchanging all 1's and 7's: 133999337137 ==> 733999331731 (prime),
exchanging all 1's and 9's: 133999337137 ==> 933111337937 (prime),
exchanging all 3's and 7's: 133999337137 ==> 177999773173 (prime),
exchanging all 3's and 9's: 133999337137 ==> 199333997197 (prime) and
exchanging all 7's and 9's: 133999337137 ==> 133777339139 (prime).
No smaller prime with four distinct digits transmutes into six other primes.
		

Crossrefs

Cf. A108386 (Primes p such that p's set of distinct digits is {1, 3, 7, 9}), A108388 (transmutable primes), A083983 (transmutable primes with two distinct digits), A108387 (doubly-transmutable primes), A006567 (reversible primes), A002385 (palindromic primes), A068652 (every cyclic permutation is prime), A107845 (transposable-digit primes), A003459 (absolute primes), A057876 (droppable-digit primes).

Extensions

a(14) and beyond from Michael S. Branicky, Dec 15 2023

A083985 If k is a number with exactly two distinct decimal digits, say a and b, neither of which is 0 (i.e., a member of A101594), define the self-complement of k, SC(k), to be the number obtained by replacing a with b and vice versa. Then a(n) = gcd(A101594(n), SC(A101594(n))).

Original entry on oeis.org

3, 1, 1, 3, 1, 1, 9, 1, 3, 1, 6, 1, 2, 9, 2, 1, 1, 1, 1, 1, 9, 1, 1, 3, 1, 6, 1, 9, 2, 1, 12, 1, 3, 1, 1, 9, 1, 3, 1, 1, 1, 2, 9, 2, 1, 1, 2, 3, 1, 9, 1, 1, 3, 1, 3, 1, 9, 2, 1, 12, 1, 2, 3, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 1, 3, 3, 1, 1, 7, 1, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 2, 1, 6
Offset: 1

Views

Author

Amarnath Murthy, May 22 2003

Keywords

Examples

			12 is the term corresponding to k = 48 as (48,84) = 1
a(7) = gcd(18, 81) = 9.
		

Crossrefs

Extensions

Corrected and extended by David Wasserman, Dec 07 2004
Offset corrected by Andrew Howroyd, Sep 29 2024

A083984 If k is a number with exactly two distinct decimal digits, say a and b, neither of which is 0 (i.e., a member of A101594), define the self-complement of k, SC(k), to be the number obtained by replacing a with b and vice versa. E.g. SC(232233) = 323322. Sequence contains numbers n such that n and SC(n) are relatively prime.

Original entry on oeis.org

13, 14, 16, 17, 19, 23, 25, 29, 31, 32, 34, 35, 37, 38, 41, 43, 47, 49, 52, 53, 56, 58, 59, 61, 65, 67, 71, 73, 74, 76, 79, 83, 85, 89, 91, 92, 94, 95, 97, 98, 112, 113, 115, 116, 118, 119, 121, 122, 131, 133, 151, 155, 166, 181, 188, 191, 199, 211, 212, 221, 223, 227
Offset: 1

Views

Author

Amarnath Murthy, May 22 2003

Keywords

Examples

			25 is a member as 25 and 52 are relatively prime, but 24 is not a member as 24 and 42 are not coprime.
		

Crossrefs

Extensions

More terms from David Wasserman, Dec 07 2004
Offset corrected by Andrew Howroyd, Sep 29 2024

A083986 If k is a number with exactly two distinct decimal digits, say a and b, neither of which is 0 (i.e., a member of A101594), define the self-complement of k, SC(k), to be the number obtained by replacing a with b and vice versa. Then a(n) = lcm(A101594(n), SC(A101594(n))).

Original entry on oeis.org

84, 403, 574, 255, 976, 1207, 162, 1729, 84, 736, 168, 1300, 806, 216, 1148, 2668, 403, 736, 1462, 1855, 252, 2701, 3154, 1209, 574, 168, 1462, 270, 1472, 3478, 336, 4606, 255, 1300, 1855, 270, 3640, 1425, 4930, 5605, 976, 806, 252, 1472, 3640, 5092, 2924
Offset: 1

Views

Author

Amarnath Murthy, May 22 2003

Keywords

Examples

			a(7) = lcm(18, 81) = 162.
		

Crossrefs

Extensions

Corrected and extended by David Wasserman, Dec 07 2004
Offset corrected by Andrew Howroyd, Sep 29 2024

A109093 Fully-transmutable primes: Transmutable primes such that each transmutation is itself a transmutable prime (A108388).

Original entry on oeis.org

139119131, 193113191, 319339313, 391331393, 913993919, 931991939, 1319999199391, 1913333133931, 3139999399193, 3931111311913, 9193333933139, 9391111911319, 11333911193113, 11999311139119, 33111933391331
Offset: 0

Views

Author

Rick L. Shepherd, Jun 18 2005

Keywords

Comments

See the definitions of "transmutable" and "transmutation" in A108388. Some primes with two distinct digits, namely all terms of A083983, can be considered trivially fully-transmutable. This subsequence of A108388 considers only transmutable primes with more distinct digits. These are primes such that all permutations of assignments of their distinct digits to their shared digit pattern produces primes. (Contrast this with the absolute primes, A003459, where all permutations of the digits themselves produce primes.). Fully-transmutable primes with three distinct digits occur in sets of 3! = 6. Fully-transmutable primes with four distinct digits, if any, would occur in sets of 4! = 24 and would also be a subsequence of A108389.

Examples

			The first six terms share the digit pattern d1 d2 d3 d1 d1 d3 d1 d2 d1. Each of these terms is a (9-digit) prime corresponding to one of the 3! = 6 bijective mappings of {1,3,9} onto {d1,d2,d3}. There are no other such primes with nine or fewer digits.
		

Crossrefs

Cf. A108388 (transmutable primes), A083983 (transmutable primes with two distinct digits), A108389 (transmutable primes with four distinct digits), A003459 (absolute primes), A108387 (doubly-transmutable primes).
Showing 1-6 of 6 results.