A231881 The digits of a(n) and a(n+1) together can be reordered to form a square; lexicographically earliest sequence of distinct positive integers with this property.

1, 6, 3, 16, 9, 4, 14, 8, 29, 5, 2, 11, 25, 12, 15, 21, 37, 69, 13, 27, 19, 26, 10, 24, 30, 42, 39, 52, 20, 34, 18, 28, 81, 43, 36, 31, 48, 7, 56, 47, 61, 33, 46, 17, 23, 40, 32, 49, 60, 57, 22, 45, 63, 54, 67, 41, 38, 44, 62, 55, 126, 58, 108, 76, 50, 92, 35, 64

Offset

0,2

Comments

A231880 and A231881 eventually merge: A231881(2539) = 2541; A231880(2540) = 2536; A231881(2540,2541,..) = A231880(2541,2542,..) = 2544,2551,.. Hans Havermann, Nov 17 2013

Links

Hans Havermann, Table of n, a(n) for n = 0..10000

Mathematica

a[0] = 1; a[n_] := a[n] = Block[{k = 1, idm = IntegerDigits@ a[n - 1], t = a@# & /@ Range[0, n - 1]}, Label[start]; While[ MemberQ[t, k], k++]; While[ Select[ Permutations[ Join[idm, IntegerDigits[ k]]], #[[1]] != 0 && IntegerQ[ Sqrt[ FromDigits[ #]]] &] == {}, k++; Goto[start]]; k]; Array[a, 100, 0] (* Robert G. Wilson v, Nov 17 2013 *)

Crossrefs

A variant of A228407. Cf. A231880.

Sequence in context: A236415 A267831 A328011 * A229005 A067990 A174012

Adjacent sequences: A231878 A231879 A231880 * A231882 A231883 A231884

Keyword

nonn,base

Author

N. J. A. Sloane, Nov 17 2013, based on a posting to the Sequence Fans Mailing List by Andrew Weimholt, Nov 12 2013

Extensions

Corrected and extended by Hans Havermann, Nov 17 2013

Status

approved