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

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

1,1

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.

Links

Table of n, a(n) for n=1..24.

Example

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.

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 *)

Prog

(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}

Crossrefs

Subsequence of A008591.

Cf. A002378, A069567, A227692, A228133, A228135.

Sequence in context: A205176 A205275 A133968 * A333746 A251111 A205834

Adjacent sequences: A337781 A337782 A337783 * A337785 A337786 A337787

Keyword

nonn,base

Author

Antonio Roldán, Sep 21 2020

Status

approved