A102832 Number of n-digit squares which contain the string "666" but not "6666".

0, 0, 0, 0, 0, 0, 3, 21, 78, 302, 1139, 4156, 14791, 52529, 183565, 635691, 2183533, 7314869, 25303217

Offset

1,7

Links

Table of n, a(n) for n=1..19.

Mathematica

fQ[n_] := StringPosition[ ToString[n^2], "666"] != {} && StringPosition[ ToString[n^2], "6666"] == {}; t = Table[0, {20}]; Do[ If[ fQ[n], t[[ Ceiling[ Log[10, n^2]] + 1]]++ ], {n, 3162277661}]; t (* Robert G. Wilson v, Mar 10 2005 *)
t6[digs_]:=Module[{a=Floor[Sqrt[10^(digs-1)]], b=Floor[ Sqrt[ 10^digs]]}, Count[ Range[a, b]^2, _?(SequenceCount[IntegerDigits[#], {6, 6, 6}]> 0&&SequenceCount[IntegerDigits[#], {6, 6, 6, 6}]==0&)]]; Table[ t6[n], {n, 20}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 26 2021 *)

Crossrefs

Cf. A052041, A075415, A102807 A032746.

Sequence in context: A067002 A110450 A176646 * A112851 A253943 A034490

Adjacent sequences: A102829 A102830 A102831 * A102833 A102834 A102835

Keyword

nonn,base

Author

James R. Buddenhagen, Feb 27 2005

Extensions

a(13)-a(19) from Robert G. Wilson v, Mar 03 2005

Status

approved