

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.


7



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
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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 bfile) by Jon E. Schoenfield, Dec 22 2013


STATUS

approved



