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 1-2 of 2 results.

A160851 Numbers which are a difference of two of their own anagrams.

Original entry on oeis.org

459, 495, 1089, 1269, 1467, 1476, 1503, 1530, 1692, 1746, 2385, 2439, 2493, 2502, 2520, 2538, 2691, 2853, 3285, 3501, 3510, 4095, 4392, 4590, 4599, 4671, 4698, 4797, 4896, 4932, 4950, 4959, 4968, 4977, 4986, 4995, 5238, 5382, 5409, 6147, 6174, 6921, 8019, 8091
Offset: 1

Views

Author

Claudio Meller, May 28 2009

Keywords

Comments

An anagram of a number k is a number formed by one of the k! permutations of its digits.
All terms are divisible by 9. - David A. Corneth, Jun 06 2025

Examples

			459 = 954 - 495;
495 = 954 - 459;
1089 = 9108 - 8019;
1269 = 2961 - 1692;
1467 = 7641 - 6174;
1476 = 6147 - 4671;
2538 = 5823 - 3285;
6174 = 7641 - 1467;
10989 = 91908 - 80919;
12969 = 29961 - 16992.
		

Crossrefs

Programs

  • PARI
    \\ See Corneth link
  • Python
    from itertools import permutations
    def ok(k):
        anagram = {int(''.join(p)) for p in permutations(str(k)) if p[0] != '0'}
        anagram.discard(k)
        return any(a != b and a - b == k for a in anagram for b in anagram)
    print([k for k in range(10, 10000) if ok(k)]), #Gonzalo Martínez, May 28 2025
    

Extensions

Definition edited by R. J. Mathar, May 30 2009
a(1), a(5)-a(15) inserted by Gonzalo Martínez May 28 2025

A384708 a(n) is the smallest integer k such that k is the sum of exactly n distinct permutations of k, all having the same number of digits as k.

Original entry on oeis.org

1, 954, 4617, 5112, 8136, 67104, 76011, 90216, 910107
Offset: 1

Views

Author

Gonzalo Martínez, Jun 07 2025

Keywords

Comments

There is no such k exists for n >= 10, since the sum of 10 or more distinct permutations of any integer k, with the same number of digits of k, will always be greater than k itself.

Examples

			a(1) = 1, since 1 = 1.
a(2) = 954, since 954 = 459 + 495.
a(3) = 4617, since 4617 = 1467 + 1476 + 1674.
a(4) = 5112, since 5112 = 1125 + 1215 + 1251 + 1521.
a(5) = 8136, since 8136 = 1368 + 1386 + 1683 + 1836 + 1863.
a(6) = 67104, since 67104 = 10467 + 10476 + 10647 + 10674 + 10764 + 14076.
a(7) = 76011, since 76011 = 10167 + 10176 + 10617 + 10671 + 11067 + 11607 + 11706.
a(8) = 90216, since 90216 = 10269 + 10296 + 10629 + 10692 + 10962 + 12069 + 12609 + 12690.
a(9) = 910107, since 910107 = 100179 + 100197 + 100917 + 100971 + 101079 + 101097 + 101790 + 101907 + 101970. - _David A. Corneth_, Jun 12 2025
		

Crossrefs

Subsequence of A384433.
Cf. A055098.

Extensions

a(9) from David A. Corneth, Jun 12 2025
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