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 1-4 of 4 results.

A173095 Partial sums of A108810.

Original entry on oeis.org

10153331, 20326464, 30559685, 40871218, 51193539, 63296870, 75460003, 87623334, 99816467, 112128400, 124441719, 139544852, 154778073, 170089706, 185421637, 200754756, 216907889, 233061220, 249234353, 265565884, 281897715
Offset: 1

Views

Author

Jonathan Vos Post, Feb 09 2010

Keywords

Comments

Partial sums of self-describing primes, where the digits are described in any order, whereas in A047841 they must be described in increasing order. The subsequence of prime partial sums of self-describing primes begins: 10153331, 75460003. What is the smallest value in the subsubsequence of self-describing prime partial sums of self-describing primes?

Examples

			a(7) = 10153331 + 10173133 + 10233221 + 10311533 + 10322321 + 12103331 + 12163133 = 75460003 is prime. a(21) = 10153331 + 10173133 + 10233221 + 10311533 + 10322321 + 12103331 + 12163133 + 12163331 + 12193133 + 12311933 + 12313319 + 15103133 + 15233221 + 15311633 + 15331931 + 15333119 + 16153133 + 16153331 + 16173133 + 16331531 + 16331831.
		

Crossrefs

Formula

a(n) = SUM[i=1..n] A108810(i).

A047841 Autobiographical numbers: Fixed under operator T (A047842): "Say what you see".

Original entry on oeis.org

22, 10213223, 10311233, 10313314, 10313315, 10313316, 10313317, 10313318, 10313319, 21322314, 21322315, 21322316, 21322317, 21322318, 21322319, 31123314, 31123315, 31123316, 31123317, 31123318, 31123319
Offset: 1

Views

Author

Ulrich Schimke (ulrschimke(AT)aol.com)

Keywords

Comments

A digit count numerically summarizes the frequency of digits 0 through 9 in that order when they occur in a number.
This uses a different method from A108810. Here the digits are described in increasing order, whereas in A108810 they can be described in any order.
This sequence is finite, since T(x) < x for every x with at least 22 digits. Last term is a(109) = 101112213141516171819. - Schimke
A character in the Verghese (2009) novel declares that 10213223 "is the only number that describes itself when you read it." - Alonso del Arte, Jan 26 2014

Examples

			10313314 contains 1 0's, 3 1's, 3 3's and 1 4's, hence T(10313314) = 10313314 is in the sequence
The entry 3122331418, for instance, is a member since it is indeed made up of three 1's, two 2's, three 3's, one 4 and one 8.
		

References

  • J. N. Kapur, Reflections of a Mathematician, Chapter 33, pp. 314-318, Arya Book Depot, New Delhi 1996.
  • Abraham Verghese, Cutting for Stone: A Novel. New York: Alfred A. Knopf (2009): 294.

Crossrefs

Cf. A005151, which is the sequence 1, T(1), T(T(1)), .. ending in the fixed-point 21322314.

Extensions

Entry revised by N. J. A. Sloane, Dec 15 2006

A109776 Self-describing numbers: reading the number gives a (possibly redundant) description of the number.

Original entry on oeis.org

22, 4444, 224444, 442244, 444422, 666666, 10123133, 10123331, 10143133, 10143331, 10153133, 10153331, 10163133, 10163331, 10173133, 10173331, 10183133, 10183331, 10193133, 10193331, 10212332, 10213223, 10232132
Offset: 1

Views

Author

Jud McCranie, Aug 15 2005

Keywords

Comments

From Robert G. Wilson v, May 05 2012: (Start)
If abcd... with a, b, c & d integers, then so is cdab... . As an example, since 10123133 is a term so must be 10123331, 10311233, 10313312, 10331231, 10333112, 12103133, 12103331, 12311033, 12313310, 12331031, 12333110, 31101233, 31103312, 31121033, 31123310, 31331012, 31331210, 33101231, 33103112, 33121031, 33123110, 33311012, 33311210.
Therefore 10123133 can be said to be the progenerator or the primitive self-describing number.
Also if we index the number abcd... from left to right, the sum of the odd indexes must equal the number of digits for unique even-indexed digits.
Number of terms < 10^2n: 1, 2, 6, 1043, 5498, ..., .
This sequence is finite with the last term is probably 9998979595959595848484848484848476737373737373736262626262625151515110.
(End)

Examples

			"22" does indeed consist of "two 2's".
		

Crossrefs

Programs

  • Mathematica
    fQ[n_] := Block[{id = IntegerDigits[n]}, If[ OddQ[ Length[id]], Return[False], Union[Reverse@# & /@ Tally[id]] == Union@ Partition[id, 2]]]; k = 1; lst = {}; While[k < 10^7, If[fQ@ k, AppendTo[lst, k]; Print[k]]; k++]; lst (* Robert G. Wilson v, Apr 27 2012 *)

A173101 Self-describing semiprimes.

Original entry on oeis.org

22, 10183133, 10183331, 10213223, 10313317, 10322123, 10331831, 10331931, 10333117, 12183133, 12183331, 12193331, 12311033, 12311633, 12311833, 12313318, 12331031, 12333115, 12333119, 14103331, 14153331, 14163133, 14173133, 14183133, 14193331, 14311533, 14311633
Offset: 1

Views

Author

Jonathan Vos Post, Feb 09 2010

Keywords

Comments

This is to A001358 as A108810 is to A000040.

Examples

			a(1) = 22 because "22" does indeed consist of "two 2's" and 22 = 2 * 11 is semiprime. a(4) = 10213223 because 10213223 consists of one "0", two 1's, three 2's, and two 3's; and 10213223 = 41 * 249103 is semiprime.
		

Crossrefs

Formula

{A109776 INTERSECTION A001358}. a(n) = n-th integer k such that OMEGA(k)=2 where OMEGA(n) is the sum of the exponents in the prime decomposition of k, and reading the number (in base 10) in successive pairs of digits gives a (possibly redundant) description of the number.

Extensions

More terms from Giovanni Resta, Aug 14 2019
Showing 1-4 of 4 results.