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.

A228133 Smaller of two consecutive fourth powers which are anagrams of each other.

Original entry on oeis.org

256, 3801203878441216, 37676241378424125849856, 458674242952187370600625, 544126177359173833650625, 685460284523397245894656, 1608863370428370905668561, 3002790971698825459360000, 25230797696265342385603441, 287990971036503268357824016
Offset: 1

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Author

Michel Lagneau, Aug 12 2013

Keywords

Comments

Given the n-th fourth power, it is occasionally possible to form the (n+1)-th fourth power using the same digits in a different order.
"Anagram" means that both fourth powers must not only use the same digits but must use each digit the same number of times.

Examples

			256 and 625 are two successive fourth powers.
		

Crossrefs

Programs

  • Maple
    with(numtheory):for n from 1 to 2000000 do:p1:=n^4:p2:= (n+1)^4:pp1:=convert(p1,base,10): pp2:=convert(p2,base,10):n1:=sort(pp1):n2:=sort(pp2): if n1=n2 then printf(`%d, `,p1):else fi:od:

A337784 Smaller of two consecutive oblong numbers which are anagrams of each other.

Original entry on oeis.org

23256, 530712, 809100, 11692980, 17812620, 20245500, 22834062, 23527350, 29154600, 83768256, 182236500, 189847062, 506227500, 600127506, 992218500, 1363566402, 1640209500, 2175895962, 2422657620, 2477899062, 2520190602, 3041687952, 3764129256, 4760103042
Offset: 1

Views

Author

Antonio Roldán, Sep 21 2020

Keywords

Comments

All terms are multiples of 9.
The indices of these oblong numbers are 152, 728, 899, 3419, 4220, 4499, 4778, 4850, 5399, 9152, 13499, 13778, 22499, 24497, 31499, 36926, 40499, 46646, 49220, 49778, 50201, 55151, 61352, 68993.

Examples

			530712 is in the sequence because it is an oblong number, 530712 = 728 * 729, and the next oblong number, 532170 = 729 * 730, is an anagram of 530712.
		

Crossrefs

Subsequence of A008591.

Programs

  • Mathematica
    s = {}; o1 = 1; d1 = Sort @ IntegerDigits[o1]; Do[o2 = n*(n + 1); d2 = Sort @ IntegerDigits[o2]; If[d2 == d1, AppendTo[s, o1]]; o1 = o2; d1 = d2, {n, 2, 70000}]; s (* Amiram Eldar, Sep 21 2020 *)
  • PARI
    ok(k) = {my(b, m=0); if(issquare(4*k + 1), b=truncate(sqrt(4*k + 1) - 1)/2; if(vecsort(digits(k)) == vecsort(digits((b + 1)*(b + 2))), m = 1)); m}
Showing 1-2 of 2 results.