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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A165411 Primes p such that each of p's digits d appears consecutively exactly d times and p contains each nonzero digit up to its maximum digit.

Original entry on oeis.org

223331, 122555554444333, 224444333555551, 224444555553331, 225555544441333, 333555554444221, 555552233344441, 555552244441333, 555554444221333, 122444455555666666333, 122555554444666666333, 144446666662255555333
Offset: 1

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Author

Rick L. Shepherd, Sep 17 2009

Keywords

Comments

This sequence is a subsequence of A140057, A078348, and A108571. There are 129 terms; the largest is 7777777666666444455555223331. As 1, 122, and 221 are not prime and any such numbers whose maximum digit is 4, 8, or 9 are divisible by 3, all terms of the sequence have either 6 (1 term), 15 (8 terms), 21 (24 terms), or 28 (96 terms) decimal digits (=triangular numbers A000217(n) for n=3,5,6,7, respectively).
None of the terms have nondecreasing or nonincreasing decimal digits. - Rick L. Shepherd, Feb 23 2013

Examples

			1333444455555226666667777777 is a term because it is a prime meeting the criteria: It contains all digits 1 through 7, its maximum, each appearing in a single run of length equal to the value of the digit.
		

Crossrefs

A247700 Numbers which have d digits "d", whenever one of their digits is "d", ordered by largest digit, then by size of the number.

Original entry on oeis.org

1, 22, 122, 212, 221, 333, 1333, 3133, 3313, 3331, 22333, 23233, 23323, 23332, 32233, 32323, 32332, 33223, 33232, 33322, 122333, 123233, 123323, 123332, 132233, 132323, 132332, 133223, 133232, 133322, 212333, 213233, 213323, 213332
Offset: 1

Views

Author

M. F. Hasler, Sep 22 2014

Keywords

Comments

This sequence lists the same terms as A108571, but ordered first by the largest digit in the number, then by size. This way, a truncation to the first 1, 5, 80, 14381,... terms is this very same sequence for bases b=2, 3, 4, 5, ...

Examples

			In base 2, the only number with this property is a(1) = 1.
In base 3, this property is again satisfied by 1, but also by the 4 additional terms 22, 122, 212 and 221. They are listed "as such" (without conversion from base 3 to base 10) as a(2),...,a(5).
In base 4, there are 75 more terms (involving three digits "3"), listed as a(6),...,a(80).
		

Programs

  • PARI
    a=[];for(d=1,3,n=[10^d\9*d]; for(i=1,#a,t=vector(d+#s=digits(a[i]),j,10^j)~\10;forvec(v=vector(d,j,[1,#t]),c=0;n=concat(n,vector(#t,j,if(setsearch(v,j),d,s[c++]))*t),2));a=concat(a,vecsort(n)));a \\ M. F. Hasler, Sep 25 2014

A356369 Numbers such that each digit "d" occurs d times, for every digit from 1 to the largest digit.

Original entry on oeis.org

1, 122, 212, 221, 122333, 123233, 123323, 123332, 132233, 132323, 132332, 133223, 133232, 133322, 212333, 213233, 213323, 213332, 221333, 223133, 223313, 223331, 231233, 231323, 231332, 232133, 232313, 232331, 233123, 233132, 233213, 233231, 233312, 233321, 312233, 312323
Offset: 1

Views

Author

Marc Morgenegg, Oct 17 2022

Keywords

Comments

A version of self-describing integers (cf. A105776).
The sequence is finite.
The last term is 999999999888888887777777666666555554444333221.
This sequence contains Sum_{m = 1..9} Product_{k = 1..m} binomial( k*(k+1)/2, k) = 65191584768311709900058498136517664 terms. - Thomas Scheuerle and David A. Corneth, Oct 17 2022

Examples

			213323 is a term because the digit 1 occurs once, the digit 2 twice and 3 three times. Every digit from 1 to 3 is present.
		

Crossrefs

Programs

  • Python
    from itertools import islice
    from sympy.utilities.iterables import multiset_permutations
    def agen():
        for m in range(1, 10):
            s = "".join(str(k)*k for k in range(1, m+1))
            yield from (int("".join(p)) for p in multiset_permutations(s))
    print(list(islice(agen(), 65))) # Michael S. Branicky, Oct 17 2022

Extensions

Corrected by and more terms from David A. Corneth, Oct 17 2022

A247701 Numbers whose digits are nondecreasing and which have exactly d digits "d" whenever there is at least one digit "d".

Original entry on oeis.org

1, 22, 122, 333, 1333, 4444, 14444, 22333, 55555, 122333, 155555, 224444, 666666, 1224444, 1666666, 2255555, 3334444, 7777777, 12255555, 13334444, 17777777, 22666666, 33355555, 88888888, 122666666, 133355555, 188888888, 223334444, 227777777, 333666666, 999999999
Offset: 1

Views

Author

M. F. Hasler, Sep 22 2014

Keywords

Comments

Subsequence of terms with (weakly) increasing digits (when read from left to right) in A108571.
It happens that the last term displayed in the usual three lines of data is 999999999, but there is of course not any reason to think that this would be the last term of the sequence, it is only the largest term with 9 digits but many more follow up to the (maybe final) 122333...999, or infinitely many further terms if a convention is fixed to extend A108571 and the present sequence to digits beyond "9". (Clarification added in view of e-mail received privately.) - M. F. Hasler, Oct 04 2014
One possibility of encoding digits d > 9 in a sequence like the present one where no digit 0 occurs, is to write them as (d-9k)*10^k for 9*k < d < 9*k+10, i.e., d=10 as "10", d=11 as "20",..., d=18 as "90", d=19 as "100", etc. See the link for other variants which are more compact for larger digits. - M. F. Hasler, Oct 05 2014
Observation by R. J. Cano: The subset of terms with no digit larger than b has 2^b-1 elements. Proof: They can be coded as b-digit (nonzero, whence the -1) binary word, where the k-th bit is 1 iff digit k is present in the term. - M. F. Hasler, Oct 08 2014

Programs

  • PARI
    a=[]; N=9; for(m=1,min(N,9), a=concat(a,n=10^m\9*m); for(i=1,#a-1, #Str(a[i])>N-m && break; a=concat(a,a[i]*10^m+n))); Set(a)
Previous Showing 11-14 of 14 results.