A231880 The digits of a(n) and a(n+1) together can be reordered to form a square; lexicographically earliest sequence of distinct nonnegative integers with this property.

0, 10, 24, 3, 6, 1, 8, 14, 4, 9, 16, 12, 15, 21, 25, 2, 5, 22, 45, 18, 28, 81, 34, 20, 29, 7, 48, 13, 27, 19, 26, 11, 52, 30, 42, 39, 61, 33, 46, 17, 23, 40, 32, 49, 60, 57, 64, 35, 92, 43, 36, 31, 63, 54, 67, 41, 38, 44, 62, 47, 56, 70, 65, 74, 124, 69, 37

Offset

0,2

Comments

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

Links

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

Mathematica

a[0] = 0; a[n_] := a[n] = Block[{k = 1, idm = IntegerDigits@ a[n - 1], t = a@# & /@ Range[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. A231881.

Sequence in context: A177126 A300150 A187621 * A102089 A250797 A250583

Adjacent sequences: A231877 A231878 A231879 * A231881 A231882 A231883

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

More terms added (from b-file) by Jon E. Schoenfield, Dec 22 2013

Status

approved