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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A102357 "True so far" sequence: floor(a(n)/10) is the number of digits (a(n) mod 10) within the first n terms; a(n) is the smallest such number larger than a(n-1).

Original entry on oeis.org

10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 23, 24, 25, 26, 27, 28, 29, 30, 34, 35, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49, 50, 56, 57, 58, 59, 60, 67, 68, 69, 70, 78, 79, 80, 89, 90, 102, 103, 104, 105, 106, 107, 108, 109, 112, 113, 114, 115, 116, 117, 118, 119, 123
Offset: 1

Views

Author

Eric Angelini, Feb 21 2005

Keywords

Comments

Original definition (edited): In a(n), the last digit must be seen as a glyph and preceding digits as a number, counting occurrences of the glyph up to and including a(n). "10" reads [one '0'] and "12" [one '2'] - which are both true statements: there is one '0' glyph so far in the sequence when 10 is read and there is one '2' glyph when 12 is read. The sequence is built with a(n+1)-a(n) being minimal, positive, and a(n) always "true so far". This explains why there are no integers 11, 21, 22, 31 etc.: their statements are false.
Terms must increase. Without this condition we obtain A102850. - David Wasserman, Feb 13 2008
The substring ...1112,1113,1114,1115,1116,1117... appears in the sequence - which means that so far the whole sequence has used 111 '2's, 111 '3's, 111 '4's, 111 '5's, 111 '6's and 111 '7's. [Corrected (1118 is not in the sequence!) by M. F. Hasler, Nov 18 2019]
The sequence is finite. The last term is a(2024) = 8945. The largest terms ending with each digit appear to be: 5890, 8201, 8312, 8623, 8734, 8945, 7756, 6697, 6778, 5979. - Chuck Seggelin, Feb 22, 2005 [Corrected '8495' but other terms unverified. - M. F. Hasler, Nov 18 2019]
When this sequence terminates there are 624 zero, 822 ones, 834 twos, 864 threes, 874 fours, 894 fives, 779 sixes, 697 sevens, 697 eights and 617 nines. - Robert G. Wilson v, Feb 22(?) 2005

Crossrefs

Cf. A102850.

Programs

  • Mathematica
    a[0] = {}; a[n_] := a[n] = Block[{k = Max[a[n - 1], 0], b = Sort[ Flatten[ Table[ IntegerDigits[ a[i]], {i, 0, n - 1}] ]]}, While[ Count[ Join[b, IntegerDigits[ IntegerPart[k/10]]], Mod[k, 10]] != IntegerPart[k/10], k++ ]; k]; Table[ a[n], {n, 63}] (* Robert G. Wilson v, Feb 22 2005 *)
  • PARI
    c=Vec(0, 10); a=10; for(n=1, 2024, while(a\10<=c[a%10+1] || a\10 != c[a%10+1]+#select(d->d==a%10, digits(a)), a++); [c[d+1]++|d<-digits(a)]; print1(a",")) \\ M. F. Hasler, Nov 18 2019

Extensions

Chuck Seggelin and David W. Wilson both computed the full 2024 terms
Offset corrected by Nathaniel Johnston, May 17 2011
Edited and shorter definition from M. F. Hasler, Nov 18 2019

A271642 Alphabetically first list of self-describing statements about the letter-type content of the list itself.

Original entry on oeis.org

101, 102, 415, 515, 505, 506, 805, 522, 103, 414, 806, 809, 815, 507, 1805, 807, 808, 1509, 418, 1506, 814, 1107, 822, 1108, 1122, 518, 412, 1806, 1115, 1514, 1520, 1814, 1820, 1508, 5705, 1522, 521, 104, 1415, 818, 1807, 1515, 918, 1907, 110, 111
Offset: 1

Views

Author

Eric Angelini and Hans Havermann, Apr 11 2016

Keywords

Comments

To decode the sequence, start by replacing the last two digits of a term by a letter of the English alphabet (01=A, 02=B, 03=C, 04=D, ... 26=Z); one gets for the first 11 terms 1A,1B,4O,5O,5E,5F,8E,5V,1C,4N,8F,... Now replace the remaining numbers by their English name: ONE A, ONE B, FOUR O, FIVE O, FIVE E, FIVE F, EIGHT E, FIVE V, ONE C, FOUR N, EIGHT F,... This succession of words is the alphabetically first one describing, step by step, the true state of the list so far.
In the first 100000 terms of ONE A, ONE B, FOUR O,..., no term ever starts with T and only one term (#13886) starts with S: SIXTY-FIVE THOUSAND TWENTY-SEVEN E. - Hans Havermann, Apr 14 2016

References

  • This sequence was mentioned for the first time on the math-fun forum on April 10th.

Crossrefs

This is the equivalent (in English) of A102850.
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